Romex and breaker switches

I currently use 2 runs of 10-3 in one conduit for a distance of 38 feet. Of course you must use 20 amp breakers and receptacles.
Worting with the very stiff 10 ga, I went with surface mounted boxes. With the depth of the box in the wall cavity and the depth of the surface box, I had more than enough space to properly fold the 10 ga into the box with no damage to the receptacles.

audioslain02. It is perfectly within code to use a larger wire size, code specifies a minimum size not max. Think about it, if for example you have a long cable run of 14-2 and, doing the math you find a higher voltage drop than acceptable you would leave the breaker as is and move up a cable size to reduce the voltage drop since larger cable means less resistance.

As far as folding the cable into a standard box, larger cable is stiffer, I wouldn't recommend pigtails, I'd install a larger box to allow more room to gently fold the cable tails in.

Another question. Our living room (including / TV / surround amps / stereo system / powered subwoofer) is at the back end of our house with a peaked ceiling that does not allow for attic access, making rewiring a pain for any electrician. Our house is about 25 years old and we probably need a new breaker box as well; in truth, the whole house should be re-wired with additional circuits upstairs and down. If I wanted to add seven dedicated lines to our living room, could an electrician run the lines on the *outside* of our house and then drill through the back wall to install the separate outlets? This would involve about 50-60 foot runs from the location of our current breaker box, but would be the shortest distance from box to outlets. Our cable TV, internet and phone lines come in this way, but I don't know what the rules are for A/C. Please forgive my ignorance and thank you for your help! -Mark

Do you know Ohm’s Law?
 What voltage does an Audio Amplifier run at?
What is the Impedance of your speakers?
What would be your total (Maximum) current draw, for this circuit ( voltage )?
Then do a direct conversion from this voltage to 120 volt circuit, what is the multiplier?
What is the maximum current draw at 120 volts direct relation multiplier.

Certified Electrician work below prefered -

Stay away from big wire for 120 volt home plugs, they are not constructed physically for wire sizes over 12 gauge, no greater than 20 amps, danger!
 I’m sure that worst case scenario you would ever draw more that 13 amps at 120 volt.
Make sure all plugs are on the same buss bar in the panel, or if you do run a 20 amp circuit, wire (12/2 prefered forcing you not to have the extra hot wire to split the red and black onto seperate busses, which is a potential noise disaster), 20 amp single pole Breaker and 20 amp 120 volt plug ( or plugs as you can configure 2 duplex 20 amp plugs on the same 12/2 wire and 20 amp single pole breaker).
 Ground loop hum could be a disaster negating any benefits to having all this powerful equipment. Can be caused by cable satelite or cable TV coax, all those multi switch and amplified devices should be on the same bus also. Your cable company or satalite dealer will supply you with a coax ground isolation device, as this is most times the main culprit for audio system noise.
 Stranded copper not required ( or allowed most times) for 60 hz electrical wire.
Audio circuit conversion done by your amplifier creates the frequencies needed for audio so stranded wire for skin effect at these various frequencies is probably a good idea. ( more conductor surface area). Depending on the frequency electrical elements travel on the surface of the wire only.

@mark_hubbard
Why would you want seven dedicated lines in one room? Your house probably has 200 amp service. If you do that it doesn’t leave much for the rest of your home. You can run the AC lines outside using a conduit to protect the wires from damage!