There is no issue running 10-gauge wire for a 20-amp circuit. I have a circuit run with hand-pulled solid-core 10-gauge and high-grade conduit that is 100' from breakout box to listening room with great results. I use Oyaide R1 cryo'ed outlets and have found like others on the thread that removing my power conditioner after the fact (Furman IT-Ref20i) actually resulted in even better sound. The comments on ground potential over multiple dedicated circuits as written above are also well-founded. One suggestion I would make is to move away from Romex; there are better sounding alternatives out there in terms of both stranded and solid core options that will cost you more but be more than worth it in the long run (pun intended)!