Based on the description above you WANT the M-100. Imagine the M-80 with extended, smooth highs, deep, authoritative bass and sub-bass, expanded soundstage, more isolation and greater comfort due to the circumaural design in a package that folds up smaller than the M-80.
I keep hearing amazing things about the M100 so I'm gonna have to try it out. I'm not a fan of the styling though... too groovy and underground. I prefer class and elegance, like the Sony 1R. But if they really sound that good, I just might have to rock them with a blazer :)