I just noticed the M50s are 4dB more sensitive than the M3s. The M3s are already plenty loud at my MLP in the living room but could be louder when I'm putting around the adjacent kitchen. The M50s will likely do the trick. According to the specs, the M50s can go to 800W peak which means about 122dB at 3 feet away given their 94dB sensitivity. That's quite the feat! More importantly for me, there is no bump around 100Hz which means they'll be more compatible with my room.

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