I think RMS power= total (peak) power divided by the square root of two.

Not only do they usually list total power, but as ken mentioned they typically add power for all of the channels which makes no sense.

so your 90wpc * 7 channels= 630 watts + the wattage of your subwoofer. multiply all of this by the square root of two and then maybe you'll feel better about your purchase wink

-David