I got two potential more inclusions for the list:
Lucifer's Friend - Wikipedia, the free encyclopedia
Sort of a hard rock/jazz-fusion symphonic outfit whose lead vocalist John Lawton later went on to front Uriah Heep. Not sure how influential they'd be considered, but you go listen to
Banquet and tell me they don't deserve a spot.
The Gourishankar - Wikipedia, the free encyclopedia
A pretty recent group, but these eclectic Russian proggies are doing a lot of good for the scene over there in terms of exposure and all that. Plus, anyone who can do a half-way decent cover of Gentle Giant's For Nobody on a debut album gets a thumbs up from me no prob.
