Trans-Siberian Outcast
Savaholic
Prog to me is a modern "catch all" term for anything that doesn't subscribe to the standard formula of that form of music. In rock music, that means anything outside the typical verse, verse, chorus, verse verse, etc. Jazz has a huge prog sub-genre to it. I've heard Blues and Reggae that was progressive. Classical was prog to start with; Beethoven, Bach, Wagner, they just made up their own rules of song structure as they went along.