What you describe about the lights dimming when you turn the amp on, at least in a residential setting, is actually fairly common. A large amp with the large transformer and capacitors will draw a very large amount of current albeit for a few milliseconds. That causes a voltage drop. I have a 200 amp service in my house and before I hooked the unit to either of my UPS units, the lights would dim for a brief moment. I also noticed that if I push the system really hard the lights would flicker just a little. The two ups devices fixed that. It was worth every dime.

I can't stress enough how much clean power has cleaned up the imaging and added punch to the low end. I do have some very light fan noise but the fan from the big unit is only on for a few minutes at a time. The fan for the little unit are on only when the input power is off.