Recommend Obscure Progressive Metal.

Odins Court - Deathanity
Suspyre - The Great Divide
Aghora - Formless
Anacrusis - Screams And Whispers
 
I'll assume that by the "main stuff" you mean the really obvious ones like Dream Theater, Symphony X and Shadow Gallery.

Spiral Architect
Cynic
Exivious
Scale The Summit
Aghora
Gordian Knot
Anabiosis
Atrox
Coprofago
Alarum
Blotted Science
Spastic Ink
The Fractured Dimension
Behold...The Arctopus
Electrocution 250
Electro Quarterstaff
Humanoid
Indricothere
Psychotic Waltz
Canvas Solaris
Ephel Duath
Sepia Dreamer

That's all that comes to mind at the moment.