Hey Patrick. Are you going to post your thoghts on the M3 vs the Behringers?
I [should] create a new thread detailing my experience with all these speakers. But I find it rather difficult to explain what I hear. Though I can still do my best.
I finally got my Radioshack SPL meter and using the pink noise of my reciever I found the M3's only needed a 1 db increase to match the 2030's at my position. Which is actually what I matched to using my ears and no pink noise (before I got the meter to verify).
Anyway I'm still not doing A/B tests. I just choose some material and listen. Then switch speakers and listen all over again. I'm not listening for specifics, I'm just listening; and if I happen to notice something specific I make a mental note. Works pretty well. (course it would have helped a ton to have an SPL meter all along

)
I've only spent about 2 days of serious listening between the two pairs and my thoughts thus far are this: I like the M3, a lot. It's great. But I feel the same about the 2030. The most notable thing is I felt that voices sounded just a little fuller/more realistic on the 2030. Maybe it's cause the 2030 has slightly more resolution, or maybe just because it's more neutral; I'm not sure.
Looking at Axiom's own graph, one can see the M3 is not exactly linear. That was apparent during my tests. Sometimes I liked that, other times not so much. Some high range vocals seemed slightly shrill at times. Though for movies/games (mainly sound effects) it was often a welcome addition. The M3's bass extension seemed a little better, though it's not a deal breaker IMO.
There may be other differences, but they're too subtle for me to describe so I won't even try.
Overall, I still like the 2030 the most. I find it's combination of clarity, smoothness, and neutrality just too hard to give up. I put a lot of faith into WmAx's praise for them. I had huge doubts about them for being so damn cheap ($120/pair). I'm still shocked I liked them the most.