The only real reason to run a dedicated circuit for the audio system all the way back to the panel - is to ensure the neutral is not shared with another circuit. Sometimes you will get some noise on a shared neutral.
Modern wiring (and also per last few NEC revs) requires ground fault protection on the majority of residential circuits at the breaker. And that requires home ran neutral wires. The previous practice of wiring a house would use 12/3 romax that would have two line wires, and one neutral. Now it's pretty much all 12/2.
Sooooo, depending on what circuit the electrician tired into, the load on that circuit, size of wire, length of run, shared or not shared neutral - you may have just pissed away some money for nothing gained.
Special receptacles that sound better???? Hogwash.
