I actually own a pair of M40's. I think the reason the M50's don't get much talk is because they're so close to the M60's, which are the just about the pinnacle of the "axiom sound" spectrum.
The M40's found a special place for me. I needed something for a smaller sized room (so I wouldn't have to stick it too far out from the wall) and offered a full range for a low price. Initially I was looking at the M3's and M22's, and quickly realized that could never own speakers with stands.
Actually, to be more precise, I was almost sold on the M22's but then started looking at the M40's. The price was right about the same, and one would need stands and probably a subwoofer much sooner than the other one would... so I looked (exhaustively) at other reviews on this forum, and knowing my personal tastes - I decided on the warmer sounding speaker.
The M40's I think are very good for me. They are a very compact tower that is perfect for small to medium rooms without a sub (although I think about one from time to time)... the vocals are just amazing through them, although I could see how someone might call them a tad "rich," but I think it boils down to personal preference.
Plus, I get zero "listening fatigue" from them, and I listen to them pretty much all the time. More importantly, my girlfriend does not either, and she is sometimes very sensitive to some of my more abrasive semi-experimental music.
As a disclaimer, I also prefer the warmer sound of vinyl to CD - so I think this also biases me towards the warmer side of the Axiom spectrum. I know some want absolute clarity, etc. but there is a point to where, I think, you are getting the full range of the music. It is then up to the listener to decide how s/he wants the music colored, because there is no "true" transparency. Like a friend once recommended to me, "Never read a publication that claims to be politically neutral. Read the biased ones, at least they are honest." I mean, I've see thousands of live performances - I go through stretches where I see 4-6 a week, and no music recorded sounds very "live" - it's all interpreted - so strive for clarity, then interpret at will I say.
Oh, and btw - that little tirade only applies to music - I don't do H/T... which I realize is the forum I'm posting in, but I thought it might be relevant.
