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 I've always said, the early bass drop-off of the M2 can be a great advantage compared to the extended bass range of the M3 and M5. The M3 and M5 may go boom in smaller rooms. Now of course if you plan on using room correction, bass boom will likely not be a problem.
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.
Do you see the light green horizontal line that Axiom included in the graph below? That line is at ~ 6.3 Ohms. Axiom chose to call the M5 an 8 Ohm nominal speaker but it is really 6.3 Ohms nominal. Why did Axiom place the line at 6.3 Ohms? Because the IEC method of specifying nominal loudspeaker impedance calls for the minimum impedance to not fall below 80% of nominal. 80% of the nominal 6.3 Ohms is the approximately 5 Ohms which occurs in the valley between 150 Hz and 300 Hz.
https://www.axiomaudio.com/pub/media/catalog/product/m/5/m5hp-impedance.png
