In addition to my Technics KN5000, I also own the General Music Piano Expander Sound Module. In one word - the acoustic piano sample is 'awesome'. I'm sure the WK2 and WK4 uses a similar acoustic piano sample so as far as the piano sound, I'm sure you can't go wrong with General Music.
Prior to purchasing the KN5000, I used my General Music Piano Expander sound module along with a 76 note weighted action keyboard controller (Fatar 1176) for all my gigging. The great thing about the General Music Piano expander is the (optional) three pedal unit- sustain, sostento and soft (una corda) pedal which really do work great. When the sustain pedal is pressed, it changes harmonic sound of the sustain depending on how much (far down) you press the pedal. You can actually hear the dampers moving away from the piano strings as you press the pedal.Great for solo piano (especially classical/jazz). I really think that the General Music acoustic piano samples 'can't be beat'.
The piano sample on the KN5000 is not great for solo piano work but when used to play along with backup arrangements (especially with just drums/bass -small combo styles)I think it is superb. For solo piano, I require a piano sound with more richness and guts (Roland samples) but for arranger keyboard jazz combo style playing, I appreciate the KN5000's clean clear mid-range harmonics which enhance your left hand playing piano comping rhythms and higlight the solos you play with your right hand.
I must admit that I don't drag out the weighted keyboard controller anymore for solo gigs because it's not worth a sore back the next day.
[This message has been edited by Scottyee (edited 09-28-2000).]