Receiver power ratings are typically based on single channel driven and while this may be mentioned in the fine print, manufacturers tend to be very deceptive. For example they may have a receiver that is 100 watts x 7 channels and call it "700 watts" when in fact it may be less than 200 watts total. If you listen to only one channel you can get up to 100 watts but if you listen to all 7 it must divide that less than 200 by 7 for less than 28 watts/ch. Depending on demand, you may get more than that at any one instant, the power is not regulated to any particular amount per channel, it's more of a first come first serve. If for example it's a quiet scene in the movie and all channels are using only a small amount of power and then suddenly something happens that demands a lot of power in only one speaker, that one channel may still get up to 100 watts. If however it is a very noisy scene and all speakers are playing loud, the single power supply in the receiver cannot provide 100 watts to each of the 7 channels all at the same time.
