Ed, I own the M50's. Although I have never owned the M22 I highly recommend the M50's. The soundstage is great. It almost doesn't matter where I sit when listening to them. My ear is not quite as sophisticated as most in this forum, but I know what I DON'T like. I am probably 80% HT and 20% music. Most of the music I listen to is 2 channel and it sounds great. I was listening to Uncle Kraker's tune Follow Me the other day. It has a good amount of acoustic guitar in it. I kept thinking I was hearing this strange popping sort of noise from my M50's. Turns out it was just the guitarists fingers sliding up and down the strings. To me that makes these speakers well worth the purchase. As a side note, when getting opinions on speakers I would strongly suggest you find out what the person owned or compared his current speakers to. I had a Bose acoustimass 7 setup and bought the Axioms sight unseen (or unheard). I am very happy with my "risky" purchase.
I am just the opposite of Jason, I have the M22's and have never heard the M50's. I absolutley love my M22's for alot of the same reasons Jason likes his M50's. I upgraded from an Energy Take 5 system and while I thought the Energy's were good, there really is no comparison with the Axioms. The imaging is so good on these speakers, that I have honestly gotten up several times to see if my center was playing, even when I knew for sure it was not on. Like Jason said, the sound of the guitarists fingers sliding up and down the strings and the singers breath are things I had never heard before.
I have them paired with a Denon 3802 and a custom built powered sub. If you want bookshelves and have a sub then I think the M22's are the right pick. If you do not want to mess with stands or are not planning on using a sub then the M50's are probably the way to go. If I had it to do all over again I probably would have bought the M50's just based on the stand issue. Either way, I think you will be very pleased. I have had two of my co-workers purchase Axiom systems (M3ti's/VP100/QS4)after hearing mine, and they are both very happy with their purchases.
I have the M50's and absolutely love them. I'll sit and listen for hours at a time, and enjoy every second of it. And everyone that I demo them to has been very impressed. I'm about 50/50 HT/music.