What to get?

i'd go with a used kurzweil. they read just about anything you pop in them and hold their value much better than any software. it can generate just about any of those tones and you can get into the editing power without paying for the name "virtual analogue".

out of what you listed however, that karma stands out i think.

The Virus C is the Shiznit for synths, basses, and just weird a$$ sounds.
Also to help answer your question, figure out what direction you want to go into next. If you want to record vocals then don't don't get a keyboard. If you have enough to make quality tracks, get a workstation.

Hey! I can input on three of these synths, since I own all of em..

Waldorf.. is it bright orange? This is the Microwave XT.. I have one. My absolute favourite. Great pads, basses, and otherworldy sounds you won't get from other synths- very unique and personal. However, it doesn't excel at modeling an analogue or anything to that extent. But for nice clean sounds it's the BOMB. I dirty mine up with a rackmount SansAmp and an Electrix Filter Factory & EQ Killer. Amazing buy. (I've seen them at Guitar Center in Boston for US$500 recently)

Nord Lead- I have the version 1 model with the revision 2 ROM. My 'go to' synth for writing because it's so quick and painless, but it just doesn't have the depth of sound my other synths do. However, it sits in a mix incredibly well and is SO useful for thickening other sounds. It also takes effects extraordinarly well..especially distortions.

Access Virus C- I have the rackmount "Rack XL" Version. It's a C in a 1-space rack. This thing probably sounds the best out of all three synths, my only real complaints with the unit are 1) it can overwhelm a mix easily. 2) slight aliasing in the hi and low end on certain patches. With the new filters, however, the Virus has let me put aside any plans of buying a real analogue synth- the OS 6.5 Moog-modeled "analogue" filters sound incredibly, very thick and meaty. Beautiful synth.

All three are good, it all depends on your style(s) of music. I do a lot of jazzy, breaks type stuff, and some chill shit too, and my setup kicks for this.. I'm quite proud of it. (I also use the MPC 2kXL , event TR-8s, and a mac running logic)

ciao,
reppo