One of the finest concert openers I've seen was on the GTR tour, when Steve Hackett and Steve Howe performed various solo and duet pieces (and that particular concert was recorded for King Biscuit Flower Hour). Steve Howe prefers steel strings, while Steve Hackett favors nylon; here's one of Hackett's more beautiful numbers:
httpv://www.youtube.com/watch?v=RUZcHZEficE
After the break, Steve gets his cheaptoy on...
"Darktown"
httpv://www.youtube.com/watch?v=Qr59QKx80X8