So the guys who bought 7500/7700 amps having hum or buzz issues all turned out be outside gear, cable box etc true? no hum from within the 7500/7700 amps?

Paul,

You are right when you take that 100 watt amp and a 200 watt amp, gut at best buy thinks 2X, but reality it 20*log(200) - 10*log(100)= 23 dB -20db =3 dB differnece in power..plus how some manufacturers measure power/THD etc not standardized

Vince