Power Cables and Wall Sockets

Run dedicated lines.

Or spend a couple of grand on a re-generator like what PS Audio offers.

IME they’re additive.  Add a better PC, you can get better sound.  Add a better outlet, you can get better sound.  Add both and you get even better sound.  I’ve said it over and over, but in this hobby EVERYTHING MATTERS and makes a difference.  And a big +1 for dedicated lines.  

If your light dim briefly at amp turn on, that's pretty normal. If your lights are dimming when using the amp your circuit is borderline overdrawn. You need to look at how extensive the line is, what other components are on it etc. A dedicated line could be helpful, a new power cord not so much. One way or another you need to lessen the overall load on the circuit. It is possible too, the outlets in the circuit are inferior and not send the "signal" very effectively. It is very much worth upgrading plugs in any circuit just to make for more robust connection etc.

@geof3 the lights dim slightly on low frequency transits when I have my system turned up pretty high, otherwise it's not noticeable. Thank you for the recommendation about upgrading plugs. I think that may be an issue. The plugs are probably 40+ years old. 

@imaninatural,

Do you have a stereo amp or mono blocks. Also what make and model.

Mike