I don't know if I'm givong the right advice ot not, but why not try out the SRJV-04 expansion board. This is the "Vintage Synth board.

Since you don't like the cold stock samples on the XP, maybe the ones on the Vintage board may be better for you. I've heard lots of good comments about this board. Anyone else here have advice to help this fellow out?

The Infamous EPU.