Well, the sounds you put into the user slots will just be reprogrammings of the stock wave forms. They will not be new sounds in the sense that it will be something like you'd get on the expansion boards.
Now, I'm not a techno musician at all, but I do have a very comprehensive set of sounds for the XP units that I downloaded off the web. Everything from synth to percussion to pads to pianos and strings and guitars to sound effects. I'd be glad to send them to you if you think you'd find them useful.