125 feet is quite a long run and you should consider using a subpanel. Even with #8 wires you will lose 3 volts at 15-amp draw. A subpanel with minimum #4 wire will limit voltage drop to a little over one volt at total current draw of 15 amps. From there go with 10/3 romex to the outlets. The 10/3 comes pretwisted and that helps eliminate common mode noise. Never run 10/2 parallel romex, that acts like an RFI antenna.
Dedicated 20a lines, 125 feet distance, which gauge wire to run?
Want to set up 4x dedicated 20-amp lines for my hifi system. The distance from the outlets to the breaker box is about 125 feet. What wires should I use? 10, 8, or 6 gauge? And should they be solid or stranded? If you could be as specific as possible that would be appreciated (brands, links, etc), as I am out of my depth here. The wire will need to run underground for a good portion, and then into craw space, if that makes any difference.