I'd like to start by saying I generally agree with what Sean is saying above. I would also like to mention that my profession is Commercial Electrician in Silicon Valley Ca. I have around twenty years experience and have installed many dedicated circuits for all sorts of sensitive equipment.
I'd like to start with a practical look at voltage drop. Why don't we plug in some real numbers that might be used for a stereo or H/T system installation. . What if we say the load is a continuos 15 amps the distance is 150 linear feet from the source (panel) copper wire is being used (k=12.9) Here's how that looks for an electrician trying to size the wire;
VD= 2 x k(resistance x circular mils/1000') x distance x load /(divided by) circular mils
VD= 2 x 12.9 x 150' x 15amps /6530(#12wire) = 8.88 or(7.4%@120volts)
VD= 2 x 12.9 x 150' x 15amps /10380(#10wire)= 5.59 or(4.6%@120volts)
VD= 2 x 12.9 x 150' x 15amps /16510(#8wire) = 3.51 or(2.9%@120volts)
VD= 2 x 12.9 x 150' x 15amps /26240(#6wire) = 2.21 or(1.8%@120volts)
I'd like to note that the allowable voltage drop from the panel to the load is 8% (NEC) So in fact a #12 wire could be used legally in this scenario.
One point I would like to make is the diminishing returns on money invested verses "bang for the buck" Running beldon wire from your panel to your load seems a little extreme to me. (If you do go this route plan on running conduit to protect the wire).
I personally would put the money into isolated grounding or dedicated neutrals.
If you buy wire and twist it together you will need to run conduit to provide protection for that wire. This may be worth the extra expense, as there appears to be some sonic benefits.
MC CABLE has the wire already twisted inside but the ground is twisted in with the hot and neutral. I'm not sure if this would hinder optimum performance? (Comments welcome)
Bumping up the wire size is a good idea. However most electricians are going to think your nuts (Myself included) if you ask them to terminate a #6 wire on a 20 amp receptacle. Especially one that is less than 200' from the panel. #8 would be the most my imagination will allow for a twenty-amp circuit.
THHN is an industry standard and personally it's all I ever use. If you go with romex I think they are making it with THHN insulation around the conductors these days though it use to be TW.
I am of the opinion that it would be better to run two or three dedicated circuits with #10 wire than one with #8 or #6 when you drop the size of the load on the circuit you will reduce the voltage drop. That is to say a 5amp load will have less VD on a #10 wire than a 15-amp load.
As far as breaker selection always match the breaker to the panel manufacturer. I personally like to use the full size breakers when ever possible.
My intention here is not to bash anyone’s comments but instead to lay down some practical wiring methods and common sense approaches. I couldn't agree with Sean more when he said "Weather anyone would want to pay for optimum performance is another story" There is a lot better ways to spend your money in this hobby so lets not be to over zealous on the dedicated circuits.
I hope this helps:~)
