Dream Theater is a superb band. Six Degrees of Inner Turbulence has to be my favorite album of theirs, so you can check that out.
Rush is another one of my favorite bands. Limelight, Closer to the Heart, Lakeside Park, The Twilight Zone; all great songs, and that's only the tip of the iceberg.
To deviate from the usual metal/rock:
76:14 by Global Communication for Ambient music. It's obscure, but it's probably one of my favorite albums to listen to.
Secret Garden for Celtic sounding classical music.
Antoine Dufour and Andy Mckee are superb acoustic guitarists. Their solo pieces need to be seen, not described. Look up "Reality," "Memories of the Future," "For My Father," and "Rylynn" on Youtube to see what I mean.
Hope that helps.