Dedicated Line

I use and have used solid core for my in wall wiring. My experience is that dedicated lines improve the system alot.
I always use 10 gauge and also use at least a quality hospital grade outlet.

Electrical code says 15A 14/2, 20A 12/2 .Wiring in wall with 10 gauge Romex is labor intensive and an inspector might not like it.All my separate/dedicated lines are 20A 12/2 with good quality receptacles on the end.
Best of luck
George

I suggest using 10/2 wire for all. Could be over kill however will not hurt anything and possibly only help.
There could be some benefits from running your electrical wiring in the following fashion:
10 gage solid THHN (white/black/green) manually (electric drill) spiral twist and snake through conduit.
I personally like to use the Porterhouse cryo'd AC outlets, which are Hubbell outlets rated for 15 or 20 amp. They are Hospital grade and deep immersion cryo treated. They are a special order un-plated version. Other outlets that have plated connectors (Nickel, Silver or Tin) that are designed to hold up in harsh chemical and / or oxygen rich environments. This is not only unnecessary for audio systems but many believe it harms the quality of sound.