Dedicated AC line with tray cable

Tray cable is an NEC wire designation. It differs from standard THHN wiring in that it uses multi-strand tin-coated soft copper. However, some use standard THHN conductors (as does Romex and BX). Whether TC Type power cable is superior to Romex from an audio perspective, that's a debate yet to be heard. One important thing: be mindful of your local electrical codes - TC wire cannot be suspended as an open cable like BX or Romex. It must be run in a cable tray system, which can add a significant cost to the installation.

I believe you would be best served to dictate to the electrician exactly what you desire, and only let him/her override you only if there's a threat of burning down your house.

IMO, Glen (the well-known electrician on this site) is very knowledgeable but is perhaps more the exception rather than the rule.

In my experience, if you should tell the typical electrician that a power cord, line conditioner, dedicated lines, etc., will improve sonic performance of your system, they will simply laugh or snicker.

In fact, some to many on this site will react the exact same way.

Based on the comments above, I'd stick with the tried and true 10 gauge OFC romex. But don't just buy the cheap 10ga at home depot. Spend $50 or $100 and get a 100 ft. spool of 10 gauge 99.95% OFC at a place like PartsExpress.com.

And while you're at it pick up some industrial duty 20 gauge wall outlets for about $20 a pop. danielwoodhead.com is suppose to have some fabulous ones for around $15 or $20.

And make certain that the electrician doesn't wire the circuits out of phase, etc.. (hot to hot, neutral to neutral).

For example: I had an electrician friend install a dedicated circuit for a few years ago. Later I went back to do swap in some audio-grade outlets. Had I not double-checked the outlet for power after tripping the circuit breaker, I would have had a nice jolt.

The electrician wired the dedicated line to the wrong 15 amp circuit breaker when it should have gone to the 20amp circuit breaker right next to it.

Sheeesh!

-IMO

The tray cable rating applies to the properties of the outer jacket for the individual conductors not the properties of the individual conductors inside. Tray rated cable is obviously intended for use in cable trays. I have 20+years experience in various power plants, up to 1000mw nukes.
Some cable trays can carry hundreds of individual cables, with each cable carrying anywhere up to hundreds of individual conductors. Common instrumentation cable is routinely 14awg with conductors in the teens per cable.
When these cables are initially installed they are probably the most abused they will ever be as they are dragged & stretched. Once installed they must dissipate heat when randomly laid in the tray on top of each other. They must then take the abuse of technicians troubleshooting which can include tools laid/dropped on them, excessive strain to move them out of the way to get to the circuit a tech is looking for, etc. Most importantly they must minimize propagation of fire. Major cable trays are often routed through dedicated "tunnels" that are more heavily protected with automated fire fighting equipment.
Tray rated cable is meant to be more rugged than Romex since it is designed for harsher environments. Generally it will be more expensive than Romex for that reason.
I'm not familiar with a code requirement that forbids installation of tray cable in a residential location but I agree that you should check with your local inspector.