M2 or M3 will be great. M5 will be greater.
The M2 is more clear than the M3 in the mid-range. And it doesn't try to play where it can't (bass). The M3 goes lower and that single bass driver also does mids but not as well as the M2. So the M2 is more linear throughout its designed range. But that also makes it sound thinner in larger, less treated rooms like yours. The M3 will certainly sound fuller and hence warmer.
The M5 eliminates the short-comings of the M2 and M3 with the HP driver and dedicated mid-woofer albeit at more expense and power demand. The M5 can also hit about 6dB higher than the M2 and M3 before audible distortion sets in.
Having said all that, I tried M2 (OW and bookshelf), M3 bookshelf, M5 (OW and bookshelf), M50, M80, M100, and ALFR in my 1920 cu.ft. living room. The M2OW won.
