The PC is still controlling what the XP80 plays is it not?
That's what's confusing us all.
Your sequencer should be able to play MIDI as well as audio.
Using MIDI all the sounds come out of the XP80, with the sounds that you want, and like, and you can even change them without distorying the sequence.
You don't have to be stuck in SoundFont mode!
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The Sonic Energy Authority - a sound investment