Stranded vs Solid Copper

Your decision on solid core is good. If you ever wanted to go stranded, Litz 9.5 awg from partsconnexion would also work great. You do need a soldering pot to prep the ends. Each individual wire has a coating. It must be removed.

If your going to build a box, do an internet search; X capacitors and Y capacitors. These little beauties remove hash from the power lines. Unless I'm mistaken, the X caps go from hot to ground, and neutral to ground. The Y caps go from hot to neutral. A world of difference almost forgotten in the diy world.

@coachpoconnor said:

I’ll look into a better breaker 

There is only one correct breaker for each panel. That is the one that is the correct current rating (regular/GFCI/AFCI) specified by the manufacturer of your panel. Any other breaker is the wrong breaker. Period.

sleepwalker65

There is only one correct breaker for each panel. That is the one that is the correct current rating (regular/GFCI/AFCI) specified by the manufacturer of your panel. Any other breaker is the wrong breaker. Period.

This is mistaken. There are instances where there are alternatives to using the OEM's breaker. For example, Siemens makes substitutes for some Square D breakers. UL listed, too. See this.

@towertone 60Hz and you’re talking about skin effect? Are you sure you’re an electrician?

Skin effect has zero role in signal transmission at audio frequencies. This is simply more snake oil promoted by cable manufacturers and their "believers." Cables are passive devices and as a result have a linear response. Only at very high frequencies, way beyond those of human hearing, does skin effect play a significant role.