Installing dedicated 10 gauge lines

I did add a high gage dedicated line and didn't hear a difference. As you have a relatively quiet load unless you have a significant distance of travel I doubt you will hear much either. Voltage drop is your enemy related to distance. There are tables to show you this and mine was 100 ft which drops a bit.

Did it myself for a couple of hundred. Inspector cared more about a child proof receptacles and the distance between wire attachment points. Was sort of snarky with me putting in the heavier wire but justified himself by saying, well I guess that is all you had. He was more impressed with the LED recessed lighting I added to around the room near the room edge.

I then added a regenerator, not a power conditioner and it was night and day. My advice would be skip the dedicated circuit if it is going to cost more than a few hundred, and invest in a regenerator which just plugs in the wall. It will normalize your voltage, no drop, patches up the tops of your sine waves, and fills in for any quick current transients. Will be such an improvement that even my wife hears the difference

Totally unnecessary to run 10 GA Romex to your hi-fi room.  The absolute most that you need (unless you have something most unusual) is 1 (one) 20 amp circuit.  That requires 12ga with ground from your panel & a 20 amp breaker.  Use a hospital grade outlet.

From that single outlet use a 15 amp or 20 amp multi outlet strip to plug in all of your gear.  Note: The only grounded component should be your preamplifier.  Use cheater plugs for everything else.  Otherwise you will be chasing ground loops to no end.  If you don't have a preamp then you will have to experiment.

It may suffice to use a power regenerator on your current outlet of choice if you are willing to spend the money for one.

Before you do any of this determine if you really need to.  Get a good quality multimeter (Fluke) and set at a suitable scale/resolution to determine if you have any voltage drop while using your equipment.  Your amp will certainly be your highest current draw AND the current draw will go up when you push the amp to high volumes especially if you have inefficient speakers.  There is really not much point in turning it up to volumes that you would never listen, but if you want a good indicator - turn it up.  A good amp with a good power supply and plenty of capacitor storage will handle the transients - that's part of their job.  You don't need to have split second resolution, but if you see the voltage slowly dropping even a couple or few volts then you might be affecting the amps performance and a remedy might make sense. Sometimes a new, high amperage subpanel close by can be a better and easier fix especially if your main panel is a distance away.  If the wire turns out to be too lite at least the electrician won't have far if the sub-panel is near by.      

FWIW, I just had a 60 amp 240 V circuit installed for my Tesla Level 2 charging station which required a run of copper that alone cost $380 for materials and the wiring came to less than $2K.

So you may want to look at electricians that specialize in EV charging.

The absolute most that you need (unless you have something most unusual) is 1 (one) 20 amp circuit.  That requires 12ga with ground from your panel & a 20 amp breaker.  Use a hospital grade outlet.

From that single outlet use a 15 amp or 20 amp multi outlet strip to plug in all of your gear.  Note: The only grounded component should be your preamplifier.  Use cheater plugs for everything else.  Otherwise you will be chasing ground loops to no end.  If you don't have a preamp then you will have to experiment.

One 20A line is certainly an option. And 12g is fine for short runs from the service panel. But to recommend grounding one component and using cheater-plugs all around is irresponsible.

And the theory for using one dedicated line is to prevent ground-loops. With all components tied to the common grounding buss bar there should be equal ground potential (impedance) unless one of the components is not using a proper grounding scheme.