I have never had problems like this with electricians other than they think I am crazy. I just installed 10 gauge Romex and use 15 amp hospitals grade or audiophile outlets either 15 amp like AudioQuest or Cardas. Typically most home subwoofers and amps do not require 20 amps.
Also, typically folks would run one direct line for components / conditioner, and one for amp… I guess you could run one for the subwoofers.
Yes, 10 gauge sounds better than 12 or 14. And get a different electrician, he clearly does not understsnd basic wiring.
@carlsbad +1
Ground loops should not be a problem unless you have two different breaker boxes and one line comes from one and one from another. If they are both dedicated lines and from the same box, there should be no problem.