Congratulations Eblack, I think you'll love them! You were in a good position because there wasn't a wrong choice among your options. And finding what you want in the B-stock is always a treat. Axiom is good on returns, there's no run-around or arm-twisting; the hardest part is taking them down and putting them in the box.
And now back to our normal thread diversion ...
I've always liked the look of the M22 over the M2. Framing it that way was insightful Mojo and rrlev.
Mojo, I wasn't emphasizing "more bass", in fact, that's what I don't like about the M3, that little mid-bass bump. It's not bad, just more noticeable than I prefer. (But I didn't return them, so not that bad.) What I was talking about is the early bass drop-off of the M2. Not a problem if you have a sub, but in the smaller room the M5 might not need the sub. And the M22 is *extremely* linear; there's no bump, just an extension down low before it drops off.
As for the impedance graph, I'm not seeing what you're seeing. Going by an "area under the curve average" (and I have no idea if that's valid for impedance), it looks like the M5s would come in at around 8 ohms assuming most music has as much over 1K as under. But more importantly, the only under-6 ohm gap I see is a small bathtub from 100-500 Hz. I snapped the line at 6 ohm because it feels like that's where amp manufacturers get antsy about speaker ratings. All that said, I'm definitely winging it; so more info on reading that chart is welcome.
