For music, M80s are really nice, although it has been a few years since I heard (SirQuack's) M80s. Without a sub, the lower end extension of the M80s is really nice.
However, I am super happy with my M60s with sub. I do plan on a second sub, but not because I am unhappy with my current setup, but because I want to incrementally improve my overall LFE experience in my theater.
I say go with what fits in your budget and never look back. The M80's are a "better" speaker by themselves, but many people would argue that the M60 fronts with a good sub (thus the low end being cross-overed out of the equation) and you would be hard pressed to hear a difference for movies.
