Damn!!! Nice price! You did great!
Ever try kicking the XS650 over a few times to see what it does?
I would spend a little time trying to get it running before you rip into it. It might not be all that hard to get going and you'll feel better know the motor is good (or at least runs). Then you can ride it and see if you even like it before you put a lot of time, energy, and money into it.