I finally made my decision, and I've gone with the M3s. Several factors played into this.
While I mainly use these speakers as computer speakers, they are the only speakers I have downstairs. As such, the M3s were better sounding in "the other rooms downstairs" than the M2s. But this is a real minor need.
Instead of rapidly swapping between the M2s and M3s, I decided to give each speaker a full 3 days of use. The M2s ARE awesome, no doubt about it. But even after EQ, I could never get the sound quite right. The M3s are a little too boomy, but that's easily dealt with by changing the EQ curve. I was also able to get some mid-pop as per Bridgmans advice.
Lastly, I discovered the M3s have the nice spacial effect/soundstage that I liked in the M2s. The M3s were not the correct height. When I'd intentionally slouch in my chair, my ears were the same height as the top of the 6.5" speaker. This produced a much better quality sound than I realized. That really sealed the deal.
I debated going up to the M5s and getting an amp, but I just didn't want to keep messing with this. When they make M5 computer speakers, I will probably trade up.
