You should read your original post and help answer what your real question is? The AC rated power usage is 1200Watts and your comparing a DC rated output of 1155Watts, they are not the same.

Ideally, if the amp were 100% efficient and not current limited, you would get 200W/channel out of 7 channels into 4 ohms. This is not the case since the Amp is likely heat or current limited for the 4 ohm load.

And, when I tested concert musical loading on power usage, the duty cycle of the music we were testing, including pink and white noise, never went above 50%. Meaning, if we expected 200W and set up our power sourcing for such, the reality was we only needed 100W. This was just a simple test and not conclusive of all setups.