I believe standard residential construction is 12 gauge (not 14) for outlets and 14 gauge for lighting. Some people when they put in a new dedicated circuit use 10ga wire, but keep in mind it is a pain to put those wires in standard size duplex boxes, so check with your electrician. Double grounds are a no-no, as far as I understand.
Once you get the wiring in, EVERYTHING, from audiophile outlets, to plate covers, to power cords affect the quality of sound. Good luck!