I asked you questions about distances. Why do you need, want, a sub panel? Is your equipment a long distance from your main service panel? You mentioned the sub would be 120/240V, are you planning to feed the 120V audio branch circuits from each line to neutral. Best to feed audio equipment connected together by ics from the same line. L1 or L2, not from both. If you agree, why not wire the sub 120V only? If you would, finish answering the rest of my questions.
Jim