For another data point here's my layout:
https://drive.google.com/file/d/1o7ZU0ZxGuO5gu96gLmHStV1uq4nR3M8P/view?usp=share_linkI have M80s in the location labeled 'speakers'. They are probably more than I needed but are not too much. (M60s would have been fine, Mojo was right; but dammit, I wanted M80s!) I'm using the Axiom ADA1000 and turn it up to about 1/3 to listen at about 80-85 db. There a longer than normal wire run (far corner of the room on the top-right), so that might be sucking up some juice.
That same top-right room has M5s and I find them a tad weak; but I'm only driving them with a Yamaha RX-V671, with a better amp they'd be fine. The M5's are unnecessary for my study (not shown) which is 13'x14'. But they're not too much either.
As for towers tipping over, I've not had a problem and I have to klutzy 60 lb dog and a schizoid cat that tries to jump on top on anything and everything. Axiom also sells outriggers if you want even more stabilization.
https://www.axiomaudio.com/outriggers-setSo to parrot the other opinions, you'd be fine with either M5 or M60s, it would just depend on your layout options and preference.
