My 2 cents, as a prog-metal listener:
Nevermore - Specifically their two most thrash-y albums, "Dreaming Neon Black" & "The Politics of Ecstacy." Loud, technical, hardcore, & I love em. :)
Candiria - Zamiel also mentioned these guys; they call themselves "urban fusion," which is essentially a blend of metalcore, jazz fusion, and hip hop. Listen to "The COMA Imprint" (probably their most diverse album) if you can stand the growling vocals.
Threshold - More prog than metal, but still worth taking a listen to if you only like harder music. Check out the songs "Eat The Unicorn" and "Fragmentation" for a taste of what they sound like with each of the two vocalists they've had throughout their musical career thus far, or, for more adventurous listeners, the entire album "Extinct Instinct."
Shadow Gallery - Again a little more prog than metal, but worth mentioning because their concept album "Tyrrany" is up there on my top three favorite albums. It's one of those albums that you need to listen to all the way through to get the full effect.
Psychotic Waltz - The quintessential technical metal band IMO. Fans of more traditional metal (in the vain of, say, early Metallica) will want to check out the album "Bleeding", while proggers like myself will also like "Into the Everflow" and "Mosquito."
Opeth - Cuz everyone who considers themselves a metalhead needs to own at least one album from these guys. "Blackwater Park" is widely considered to be their best, so check it out! (warning: more scary growly vocals)
Devin Townsend - Nearly everything Devin touches turns to gold, from the wacky death-metal of Strapping Young Lad, to his awe-inspiring solo albums, and many weird side projects. I like his solo works (specifically "Ocean Machine Biomech" and "Terria") the best, and each is worth your time/money.
Well, that's my recommendations... off to class now! *runs away*
