15 amp circuit VS. 20 amp Circuit

@joshziggie2021 Don't lisen to @impaler he doesn't know what he is talking about, you will get better performance from your equipment with dedicated 20 amp  circuits. The problem with people who use math on this type of problem is they don't realize just how much the current draw is for really short durations, you can't measure it with a multimeter.

outlets are always in parallel.

invalid

Sorry to agree to disagree. What you are referring to is the instantaneous peak load response and what you would call droop in that particular measurement, measured in microseconds. To some extent effected by wire gauge and contact resistance in the power delivery circuit, source impedance etc. My point was you would need a great deal of that differential to notice a 15 or 20 amp circuit difference. This can be verifiable if you want to take it to that level. Sometimes sound science and engineering are good things so people aren't wasting their money on snake oil. Again no disrespect to your opinion.

joshziggie2021

In your particular case, I am indeed puzzled by the specs you are stating. 4kW for subs and 3.4kW from other amps? This represents a truly incredible amount of energy and, in your case if you are experiencing anywhere near these load values, that would best be served by a minimum of a 60 amp circuit at 120VAC, (30 @ 220VAC)Running 6 or 8 AWG cable. Those load values would be similar to a sound reinforcement system for a small stage. Please guys, I do this for a living. I'm very much all about a solid power supply system, but science and math should dictate, not guesswork. 

I feel we often confuse the Watts rating of our equipment with the real world power they use.  I have two Hegel H30 mono amps rated at 1150 watts each.  In theory, I require 19 amps just for these.  I can tell you that they only draw about 5 amps combined when I am running them.  With all the equipment the OP is using, I can see the need for more than one 15 amp breaker.  I could be wrong but I would bet the sub amps are D Class and don't draw anywhere near 8 amps (1000/120).  Your dimming lights suggest another breaker is required but the fact you're not constantly tripping the current 15 amp breaker tells the tale.  

bigtwin

Exactly correct, wattage rating for a particular appliance is a UL/CE requirement based on very specific tests and results. As I mentioned, those power levels (continuous) are unheard of in home audio. The dimming lights is another issue altogether, and the breaker size isn't going to help that. This is a source power issue, and could be poor connections in the primary feed, under-rated house/apt current supply, generally lower than normal voltage at source, or even an under rated/over utilized transformer at the pole. You have to id the problem before you can fix it.