Note that the 710,780 numbers aren't "actual power draw" at full rated power. This would be the case only when explicitly stated(rarely so)to be at "full power" or similar language. Otherwise this is at an average power output which is typically 1/8th of full power. Class AB amplifiers are about 50% efficient at full power but about 20% efficient at 1/8th power. This equates in this case to about 150 total watts of all-channel 1/8th power output, which requires the 710/780 watt input numbers at about 20% efficiency.

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Enjoy the music, not the equipment.