Dedicated power to audio system—how extreme to go?

Inspired by this post on the What's Best forum, I got to thinking about a truly dedicated circuit feeding the outlet where my audio stuff is plugged in. We're going to do some other work that will require a new subpanel and other electrical improvements, so this might be a good occasion to make some improvements. Right now my system feeds off the upstairs subpanel that doesn't have any big appliances on it.

 I've jiggered things around in various ways so that there's nothing else on the #12 AWG circuit feeding the audio system, although there are intermediate outlets between the breaker box and the system. The breaker has a GFI (ground-fault interrupter), and I've read that even these can have a negative sound quality impact. In the linked post people refer to "audiophile" circuit breakers, but I didn't find any for the US market. The room lighting is on a separate circuit. The house was completed in 2005 so everything is pretty modern up-to-code, but I don't know where the utility company's transformer serving us is located.

The post says you should use wire with a 4-mm cross-sectional area for 120-volt service, and according to this calculator, that translates to #6 AWG wire, and of course you'd want to get the cryo-treated, if you can somehow coil it up to get in the cryo-fridge.

But seriously, if anyone has experience with a true breaker-box-to-outlet dedicated electrical service, I'd like to hear about it.