Not Prog but you need to check out Steve Stevens. One of the most amazing guitars players I've seen. Considering his known reume is Billy Idol and Vince Neil, so many would write him off. Don't. So Good.

Here a YouTube link of an acountic/flamenco-sih deal he did. It's tasty and he has a few jaw droppers in there too. (Also note that Derek Sherinian is keyboarding towards the end.

While it can get pretty odd, I'd check out Bozzio Levin Stevens on Magna Carta. Good stuff.