Branch wiring to to 120-volt lights and receptacles have to be on a 15 or 20-amp circuit breaker, but the wire can be any size greater than #12. That's the code - whether you choose to heed it or not is your business. General-purpose receptacles are rated for 20-amps, which is why the 20-amp max breaker size.
30 Amp Breaker Question
I want to move my system into another room. The room has three outlets and a lighting fixture. The circuit traces back to a 30 amp breaker in the box. Is there any problem using a 30 amp breker circuit with audio gear? I know a 20 amp dedicated line is better, and that will come later.