Yes Opeth is my favourite.
I also dig (in no particular order) Symphony X, Kamelot, Bloodbath, Sabbath, Mastodon, King Crimson, Arch Enemy, Al Di Meola, Devin Townsend (Band) & SYL, Scar Symmetry, Diablo Swing Orchestra, Newton Faulkner, Cynic, Santana, Porcupine Tree, King Crimson, Death...