Don't you have the editor that should be with the XV2020?
Failing that you could try this:
http://soundtower.com/xvedit/ Synths that can playback samples:
A few do, but they all come at a price.
Think Triton, Fusion, Motif, Fantom.
Seem to remember the Yamaha SY series(77, and 99 I think) that you could fit a 512K board inside which was battery backed, samples could then be loaded via MIDI (this is very slooooooowwwwwwwwwwwww).