Korg Poly800/Poly800II/Poly800mk2
Korg Poly800/Poly800II/Poly800mk2 + EX800
Modification
the best know one is the reso and cutoff mod, which can be done on the analog board http://synthmod.net/korg/fm800/ , but there's also a bigger mod available which tunes the memory number, velocity and more...
more RAM (memory) and features http://patrioticduo.tripod.com/korgpoly800ex800mkiii/index.html
Info
Poly800/EX800: http://www.sequencer.de/syns/korg/Poly800_Poly800II_Poly800mk2.html