Kurzweil K2500XS

software: OS4.04 (this is the kdfx OS). the OS is upgraded regularly and can be downloaded off the net onto a floppy and installed into your machine.
presets: presets on this machine are called "programs" and are easy to dial up and play with. the sequencer is super but is a little difficult to use because of the small screen. to be frank, this is not an easy machine to use - but mainly because it can freaking do *everything* :). i bought this thing 7 months ago and i'm still learning it. the manuals are adequate but not awesome. (i couldn't find the ouput impedances anywhere). it comes with 2 videos and there is LOTS of online help from other K users. my only real gripe in the "easy of use" category is the programming interface. you have to type in letters for names etc. on a numerical keypad. it's like trying to type a letter to someone using a touchtone phone :). the obvious solution is to make it interfaceable with a PC so you can type names and program (the sequencer especially) the thing with a real keyboard/mouse (ala Alesis). i suppose almost all synths suffer from this. someone wrote a free computer controller for it but it uses the midi port so it's useless when you want to record/transmit midi. there is an SCSI port that could be used for this, tho. maybe there's software out there i haven't found yet. (MOTU? librarians?)

my machine has: piano, orchestral, and contemporary ROM block expansions; KDFX digital effects; sampling option; PRAM upgrade; and espresso machine attachment (just kidding).
the synthesis engine is digital sample-based. 48 voice polyphony, velocity and aftertouch - 88 keys. it also has controllers up the wazoo: 2 ribbon controllers, a breath controller, sliders, buttons, wheels, 5 pedal jacks - comes with sustain pedal. the action is lighter than a piano and heavier than a cheezy casio. that's all i'm saying :) you have to try it for yourself. it's nice. the controllers and keyboard are *extremely* flexible. you can route the controllers and arbitrary sections of the keyboard to almost everything, including the KDFX effects. this is good if you play live and need to do a lot of stuff at once. (unfortunately, this thing weighs 70lbs...) out of the box, this thing is not GM friendly but it can be, through programming/stealing other ppl's programming off the net :) it can read and save sequences to midi format.
the i/o's are analog, spdif, and aes. digital i/o's are 16 or 20 bit, 44.1 or 48 KHz. there is also an optical digital input. i haven't yet tried to sample anything.
this thing can supposedly read akai, roland, and other sounds but i haven't tried to use any yet. because of the unique synthesis engine, soundware not specifically written for the Kurzweil platform won't be nearly as flexible as that programmed for the K. i'm no (V.A.S.T.) guru, but the basic idea is that a preset or "program" can use many keymaps/samples overlaid and/or interacting with each other according to a huge list of algorithms the programmer can choose from. this thing can even do virtual analog sounds well. there are many K-specific CDs out there.
the KDFX unit is a must. the default effects are incredibly noisy and are converted to analog before they go in. the KDFX option makes effects completely digital. you can even use the KDFX as a stand alone digital signal effects processor for other instruments. it has special leslie and rotary effects to support the KB3 mode which simulates a Hammond B3 with midi sliders acting as drawbars.
i wish it supported word clock or midi time code. it supports midi clock. if you're recording audio instead of midi you can use the spdif, which has timing info embedded.

in the end, the thing you will notice the most are the price tag and the sounds.
since i hate trying to describe how things sound by typing, you're just going to have to take my word for it and check it out :). the KDFX sounds great. Sweetwater Sound has several demos on their website.

it came with an intermittent bad contact on one of the unused CC foot pedal jacks which cause the volume level to drop out sometimes. i opened it up and cleaned/jiggled it, and it was gone. no other problems. i use this in my home studio. i don't gig but i'm sure it would be reliable. only problem: it's heavy.

i've never dealt with Kurzweil except thru their website. the retailer, Sweetwater Sound, was extremely knowledgeable/helpful in explaining the options. they also have a lot of K resources on their site, including many great sounding sample CD's they make specifically for the K.

i'm not giving it a 10 only because this thing costs a *buttload*. it's extremely overpriced. especially seeing as they're made in Korea? with the current exchange rate, they must be making a killing. it's a hell of a machine, but you have to decide whether it's worth the extra money, or whether you should buy an Alesis and a new motorcycle :). i was also considering the E-mu E-synth, the Korg Trinity, and the Alesis QS-8. i'd buy this again but prolly the 76 key version (no X in the model name). i never come close to needing 88 keys. but wait, that keyboard has different action. doh. maybe a K2500RS and midi controller. :)
another thing you should know: in terms of polyphony and the digital I/O there are other machines out there with more. (i.e. more voices and faster sample rates/longer word length). the SCSI port is SCSI-I and can only read CD-roms at 4x. the tradeoff however, is that this machine is STABLE. it's been debugged. it has yet to crash on me. i haven't come anywhere near using all the polyphony anyway, because i record tracks separately into cubase.

Software version 3.5x. I have found the synth architecture difficult to program and completely unituitive. I can only say, 'Thank goodness for some free tutorials on the net.' The manual is practically useless, which is incredible considering the fact that it weighs as much as phone book. The videos are about as boring as boring gets. In terms of editing the sounds, it would have been helpful if frequently used parameters, such as EG and Filter settings, could be mapped to knobs or sliders.
The presets are nice and the overall sound of this unit is what made me purchase it. Somehow it cuts through all of the "synthy" sounding keyboards.

Polyphony is advertised as 48 voices/192 oscillators, but this is actually quite misleading. You will never get 48 voices of polyphony out of this unit under normal circumstances. While the K2500 can emulate many analog sounds quite well, it often takes 2-3 voices of polyphony where a real analog would use only one voice. The reason is that a real analog has two or more oscillators per voice, whereas the K2500 can use only one osc per voice when it has a resonant filter going. Therefore, the K2500 has to use a whole new layer to get a second oscillator. Hold down a a three-note chord with each note using up two voices and there goes 6 notes of polyphony. Also, a stereo sample will use up two voices per note.
The standard built in FX is a Digitech unit basically equivalent to the ancient DSP 256 (but not quite as powerful in terms of MIDI control). It's not bad, but you'll definitely want to get the KDFX as soon as you can. The Digitech unit gets its input as an analog signal from the K2500 synth engine whereas the KDFX gets it digitally. This will have a big impact on the noise factor. Also, the KDFX interfaces back into the synth engine itself. The KDFX offers four channels of insert FX plus 3 Aux send FX. For details check out the Kurzweil web site. As far as I know, this is most powerful built-in FX unit of any synth/sampler.
The expansion capabilities are pretty impressive; check the Kurzweil web site for details. I hope that Kurzweil makes a new chip for this unit that supports more polyphony.
It's got more MIDI capability than you'll ever need.
It has an onboard sequencer, but I don't see this as being much use. Not that the sequencer itself is bad, but it gets its memory from the PRAM section instead of the sample RAM section. PRAM can be a maximum of 1.2 Mb (and I only have the stock 256K) which is shared with loaded programs. You simply run out of memory too easily, especially if you're turning knobs and pitch wheels. When the sequencer runs out of memory, it just stops playing.
One of my complaints about the sequencer is that each track can only send data to one MIDI channel. The old Yamaha QX5 was only an 8-track sequencer, but once you were done with a given musical part, you could merge it to one track regardless of channel. This allows the other tracks to operate as working areas and the 8th track is the main track, which of course could be unmerged by channel. The K2500 sequencer, with only 16 tracks should employ this technique.
The keyboard action is great. Of course, with fully weighted keys, you're looking at 72 lbs plus and Anvil case to lug around. DON'T EVEN THINK ABOUT AN SKB CASE!

As I said, the sonic quaility of this synth is unsurpassed. It has real bottom end without futzing with EQ. Somehow the clarity is so good that you don't have frequencies stepping on each other. It's great at producing a wide number of sounds, from analog to sample playback. However, even though it has a variable architecture synth engine, it's still NOT the same as Virtual Analog. For analog sounds, the Access VIRUS blows this synth/sampler away. Also when programming an analog sound, most of the time you'll be working with a single cycle sample of a square, sine or saw-tooth wave. This creates problems with portamento, pitch-bend and pulse width modulation. To get PWM you'll probably have to sample it from an analog synth.
The unit will work for any style of music, but if you're going to do techno, then you WILL need something analog or VA for flavor. One of the failings of the synth engine is that, even though you can modulate the Attack, Decay and Release time of the envelopes, you must modulate ALL or NONE of them. It's things like this that lead to frustration with programming the K2500. You expect that there will be AT LEAST AS MUCH power as what you've had with other synths, not less. So the interface frustrates you because you're hunting around for these missing pieces.
Another complaint I have is the whole arpregiator issue. The arp can only be used in multi-mode (Setup Mode). Secondly, while it has many latches, it doesn't have one like every other keyboard arpeggiator made in history. Again, you expect this unit to have AT LEAST the power of predecessor keyboards. Lastly, there's no concept of storing arpeggiator patterns and navigating between them.
With respect to expressiveness, the K2500X is unsurpassed with all of the physical controllers which are mappable to and MIDI CC.

This is worst part of the the K2500. I had to return two units. The first one had a huge dent in the chassis, the second one just died after about 12 hours of use, and the third is currently in the shop with an intermittent problem which causes the sound to drop to zero. I then have to power off the machine and power it back up. YOUNG CHANG DEFINITELY NEEDS TO ADDRESS THIS ONE.

Tech support is all right I suppose, but I wouldn't rave about it.

I still think the K2500 is a great piece of gear, but as I've come to know it better and work with it, I see that it has some flaws that I wish weren't there. My other gear includes a Matrix 6, Matrix 6R, Access Virus, Korg Z1 and Roland Super Jupiter (MKS-80). None of my other gear is really like the K2500 so I can't really make an even comparison. I bought it as a workstation synth, and as great as it is, it's not the end-all, be-all. I never thought it would be. Nothing ever is. At some point I believe I'll get a rack mount version for portablility and more polyphony.