bman, it depends on how far the MLP is, the sensitivity of the speakers, the room properties and the source material.

rrlev, with regard to the plastic inserts, I am referring to the terminals on the speakers. On the top of those terminals, there are holes that are exposed if you're not using banana jacks. My v2 had plastic caps that closed those holes.

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