i can answer your first and second question.
i have the M60's and power them with the Onkyo 701 receiver, which is 100wt per channel. the 701 powers my speakers flawlessly. it has no troubles what so ever. in fact, i have yet to crank the receiver to its complete capacity, cause its just too dang loud.
the M50's should be plenty of speaker for that size room. they will not be "big or boomy" at all. i have the M60's in a 28x26 room, and they can fill it completely.
now, as for how the 50's sound....? i have no idea, i have never heard them. but my 60's, in my opinion, sound better than the paradigms, infinities, and boston acoustics that auditioned.
maybe someone with some 50's can give a little more detailed advice.
bigjohn
