Like the M3, the M2 is rear-ported. So you'll want to keep it at least a foot away from a boundary. I had mine set up with their backs 2 feet from the front wall in my livingroom and the bass wasn't bloated or lacking. Even in my main room, when I had them 3.5 feet away, bass was good.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated