i think that all receivers have 1 power supply, that power supply is providing power to all channels of amplification, all processors for the signals ect.
the more powerful outboard amp is so that you can get the same volume without driving the amp into the clipping region on the affected channel.
the center channel is where 70% of the audio information in a movie comes from, hence the reason i was recommending a 180 to replace the current 150, and why Alan recommended an outboard amp. if you had blown the pair of m22's the recommendation would have been different.. you were trying to get the 150 to do a job it is not large enough for i think... You just need a larger speaker with more drivers.. The SVS, it depends on if you are driving it past the amplifiers limits.
This whole conversation can be boiled down to staying with in "design specifications"
I would say call axiom if you haven't already, and tell them the situation and see what they have to say. They do this stuff all day every day, and have experience with rooms such as yours i'm sure.
