I bought a K2600S brandnew in 1999 and never looked back, in fact this date marks the end of my usage of arrangers....
Mine is fully loaded.
Due to the weight I did not use the K much on stage, but my bandmembers/friends recently suggested we have to put some pinkfloyd on our lists,,, So will be used on stage a lot the coming year....
I agreed if the bandmembers will carry the board...

About the polyphony:
The only time I run out of polyphony is when I use a lot of different drum programs in one setup, which has to do with the way the drumpatches are programmed.
You can avoid or correct this by manual editing, but since we have a drummer there's no need for it on live performances.
So that's only an issue if you are composing full songs on the K.
The overall soundprograms are so good that you never need to layer sounds, so the poly48 of the K is no problem att all.
Now this board is built in 1999 and loads audio samples, akai samples etc... if you want. You can use the effects section to run a guitar through it etc...
If you don't mind a long learning curve it's still one of the best synth's on the market...
Fred