Tool & The Mars Volta ---- Not a huge fan but I can appreciate their music. Listen to em once in a while, but not all that often now though.
Porcupine Tree & Kayo Dot ---- Love em to death.
Muse and Battles(?!) ---- Rarely listen to them tbh.
Coheed and Cambria ---- Heard only a few tracks on youtube, never interested me.
Flower Kings & Oceansize ---- Like them quite a bit!
Sleepytime Gorilla Museum & Spocks Beard ---- Haven't yet listened to them.
There you go.
Also, Riverside, Pain of Salvation and Arcturus are all worth a mention.
And is there a place for 80s stuff like Marillion, Queensryche and Fates Warning?