I have a HK 235 AVR with the output split into 3 zones around my house driving 2 M22s and a Velodyne CHT-8 sub in my living room (roughly 24 X 20 X 20 = 9600 cubic feet - SPL meter used at 18 feet). I set the receiver at -5 (range -80 to +15) to listen to what I consider loud music (about 80dB). When I want to "crank it up" I can get 100+ dB. If it weren't driving 2 other zones it would be even louder... You might see if the salesman would let you try out another receiver (ideally bring home 2 models - one that is just like what you bought to compare to yours and one that is different and a very good known receiver like a Denon or HK - even if it were just a 2 channel stereo receiver...)
