Yes the M80's go lower than 60hz and quite well.
Also,it is not a hard cutoff at the crossover points. Even though your receiver is set to cross over the Lower Frequencies at 80hz there's a slope set to say -6db. The sub probably starts working at 90hz although -6db by the time the 80hz it's at equal level to the 80hz reference point of the system you adjusted before setting the crossovers. if your M80's are set at 60hz, it's a gradual roll off they still play 58hz, 50, 40hz although not very much that you would even notice.
I find it ridiculous to buy these M80 HP in a home theatre setup to cut them off at 60hz. Just seems to be a waste, if your not using the low frequencies and just using the upper bass and highs the M22 have the identical drivers that are being used and play down to 60 hz. and $2500 cheaper. For 2.0 music in 2ch ok got a case for them. And you can say the bass on the sound stage is better if in ful range, well yeh ok but most put thier subs up front on stage and if not, I am sorry I do not sit up on stage I sit 12 ft back and the subs take care of the bottom end quite fine. Now if playing at extreme volumns, 100db then yeh towers.
I think having towers is more to kill two birds with on stone cheap. unless of course your room is huge, but for a normal person my room is 12x15x7 and the M22 are quite loud as it is.