Symphony X
Savatage/ Trans-Siberian Orchestra
Queensryche (up to about 1994)
Kamelot
Circus Maximus
Pagan's Mind
Ayreon, Star One and various other projects by Arjen Anthony Lucassen
Fates Warning
Crimson Glory
Evergrey
Watchtower
Morgana LeFay
Balance of Power
Adagio
Thought Chamber
Kingsbane
Pain of Salvation
Enchant
Shadow Gallery
Opeth (growly, but still very prog)
Also, you should check out solo projects by various members of DT, most notably James LaBrie/Mullmuzzler, Liquid Tension Experiment, Transatlantic, Planet X/ Derek Sherinian and Dominici
(NOTE: I was only listing progessive
metal bands. If you are interested in checking out prog-rock, also look up Genesis, Yes, Rush, King Crimson, Pink Floyd, Gentle Giant, Saga, Spock's Beard and other similar bands)
Enjoy