As a point of reference:
My room is approx 12' x 18'
My Aperions' efficiency is 87dB and present a 4 Ohm load at some frequencies
I'm running a 970/7075 combo and it's more than loud enough although for some sources I get within 10 dB of maxing out the volume knob on the 970.

BTW my sub has a 250Watt plate amp and it's using most of that