I forgot about The Alan Parsons Project.
Underated to death,but brilliant nevertheless.'The Turn Of A Friendly Card' is an eternal classic.The band never made it as big as some other progressive rock acts,but the level of mystique assocaited with their music is something that only Pink Floyd tops for me.Honestly,when you listen to some of their music in a relaxed mood,it takes you into a different mental dimension.I know,it sounds like a lot of psychdelic horseshit,but i think everyone who has heard their stuff would agree.
Ps.Fleetwood Mac is a fantastic band.Im a much bigger fan of the Stevie Nicks era than i am of the Peter Green era.She is one of the best female vocalist/performer ever IMO.I know Janis Joplin and Alanis Morisette fans would disagree here,but Stevie is pure class.