Hard to go wrong with the 580, 780, or M50.
580: Most bass, portable, efficient, comfortable
780: Still lots of tight bass, more balanced sound, portable, efficient, comfortable
M50: Big, less portable, less efficient, More bass than 780, but still pretty balanced.
780 is my favorite. That's what I own. And the Ultrasone's have S-Logic, a nice big soundstage that sort of surrounds you.