I would also mention that while the M80's definitely put out more bass, the M60's do a pretty tremendous job on their own. I've had a few people over that have asked where I am hiding my sub... which I do not have yet. Granted my listening area is very small, which probably contributes the most to this effect.

M60x2, VP150, M22x2
Sennheiser HD-595
Onkyo TX-SR507, PS3 (40gb)