So many things to consider here. As much as i also like the idea of hearing and trying out the M100s, i know that our present room is just too small for that size a speaker.
It is hard enough to get a proper stereo image because of spacing so getting something bigger doesn't make any sense, for that room.
As previously mentioned by others, what are you trying to improve or what is your goal with the idea of going for M80s or 100s (and i am purposely NOT using the term "upgrade" here).
"Those who preach the myths of audio are ignorant of truth."