I got some very good advice about dedicated lines, including from members here and from Chris Venhaus at VH audio. Here's a compilation of some of that advice.
If there are multiple dedicated outlets...
Wires between the breaker panel and the dedicated outlets:
same type
same size
same length
be continuous (ie, no splices).
Identical wire lengths ensure that each outlet's ground path is identical and that no ground loops are created.
Wire must be:
copper, not aluminum
be 10 AWG or thicker
If you run a Subpanel it should be:
powered by a single phase from the main panel
wiring between the main panel and the subpanel should be 8 or 6AWG
Breakers in subpanel feeding audio lines:
should be silver-tungsten (not copper) contacts
Use silver paste on the breakers' screw terminals
Use silver paste on the contacts in the AC outlets that attach to the wire
McMaster #1219K57 silver paste is ideal
All contacts between breakers and wire should be clean, tight, and treated with silver paste