Only if the amp is 100% efficient.//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif NO amp in reality is like that though.just take the total amp fuse rateing and times it by the voltage supplied and youll get your wattage the amp can put out.
40a + 40a = 80amps 80amps x 12.6volts = 1008 watts