agreed on m83
http://www.myspace.com/americandollarband is a band that just sent me their cd and I have on rotation now. A more electronica version of Electric Wizard.
That was very post rock - in fact more so than electronica I think. Bands to look into are for sure are Explosions in the Sky and Mogwai. To a lesser extint Tortoise, Godspeed You Black Emperor! and Sigur Rós.