Hey guys... I'm an electrical engineer and have designed audio power amps so hopefully I can shed some light on the AC power rating versus the power output.

First of all, the most a standard 120 volt household product should be rated to draw is 1800 watts (which is the most you can safely get from a standard 15 amp household circuit). So that likely explains the 1800 watt rating on the back panel (and in the specs).

As for 300w x 7 continuous output, that would indeed require an even greater amount of power from the AC line. Most class AB audio amps are only about 60% - 70% efficient. So if we assume 70%, you have (300x7)/0.7 or a whopping 3000 watts of AC power draw!

This would require the amp to have at least two 1500 VA transformers which is unlikely. It would also cause a lot of AC line "sag" even on a 20 amp 12 guage circuit. Even if you somehow manage to provide 120 volts AC at 25 amps to the line cord, I doubt this amp will product 300 watts x 7 from all channels at once.

Running 200w x 7 out, you would still need about 2000 watts of AC but this is a more realistic number. The amp just might meet that spec (at least on the 3 channels that have a transformer to themselves) if they used 1000va min. transformers. The other 4 channels might have a harder time sharing one transformer.

In reality, however, even cranking your favorite bring-down-the-house DVD, the AVERAGE power consumed by the amp is unlikely to exceed 1000 watts even when pushing it to clipping. There will be plenty of power supply reserves to go around. This is how $299 100w x 5 receivers manage to sound as good as they do. On the test bench, with 5 channels driven, they usually only manage 35 - 50 watts/ch.

If you want more continuous power from all channels on 120 volts, you need to look at something like the Sunfire Cinema amps which are more like 90+% efficient thanks to Bob Carver's trickery. Or use 2 or 3 channel amps split up on multiple AC circuits. The big Cinepro amps (which use huge 3600 kva transformers) recommend running them on 240 volts (or a special 30 amp 120 volt circuit) if you want to get anything close to their full output power.