What type of wire for dedicated 20A AC lines?

@dancarlson10 , that’s totally an option. Since I will have two dedicated lines, I can borrow a demo Niagara 5000, and hopefully a Torus RM20 from another dealer, and if I’m really lucky, a Nordost QB8 (which isn’t a conditioner at all), and I can experiment to see what sounds best. Including simply connecting my amp straight to the wall. Nordost support has told me multiple times to be cautious with conditioners with amplifiers. While they generally work if they are designed to supply the necessary instantaneous current, Nordost says they change the tonal balance. Which I heard first hand trying the small AC line filtering device from Shunyata (Venom Power Defender). That device cleaned up the sound a bit, but also decreased lower frequencies while raising the upper frequencies, at least in my system. I don’t need or want my tonal balance changed, if I can help it!  Of note, Nordost twice now has told me that if a conditioner is really needed to deal with noise, that Torus is a good brand, or “I’ve heard good things about Torus”, but of course cautioned me to try first due to tonal impacts.

@nyev 

I have a QB8 and my amp is plugged into it. I haven’t noticed any negatives from doing it this way. Good luck! 
 

Ron 

Speaking as a former master electrician I would just run 12-2 WG for each line and save the extra money to spend on a good power conditioner. That is all you need.Voltage drops don't come into play until you get around 100 feet runs.

My two cents. Much of what is advocated (large diameter wire, solid copper, etc) is technically **true** but of almost zero incremental value, or, in other cases, "a given" whit US and EU code at least.

I do have a 20A home run from my main panel to a single, quad outlet in my music room.  I do have hospital grade outlets in it (a big $30 or so).  It is 12 gauge (but code demands it  anyway!).  It is copper (but any quality romex or BX is copper). yes you want it off the phase, but why would anyone create a 20A single phase circuit from two? Mysteries abound.

I do advocate a noise filter of some form, a very large isolation transformer or a low pass filter that essentially removes noise. 

Most of these are fairly minor improvements, more a "lack of issues". yes your amp will have a boig power supply and remove much noise.  But the lower the starting point the lower the ending point - all power supplies are filters that can be characterized in dB loss at a given frequency - low in, lower out.  Iso transformers are a trade off - great in theory, but you need to over spec them (i'd say 2 kW) and some general mechanical noise.

This is not about moving more current. That comes from your power supply, either C or LC.  And the current you can move through 14 guage (even 16!) is HUGE relative to what you need.  Code covers the limits already.  Honestly, crap outlets (bad connections) re among the worst problems, along with old, creaky wiring both in and outside your house. Most modern subdivisions are fine.  My public wiring is >70 years old (but meh, still basically fine).

The other BIG DEAL is avoiding ground potential differences (loops). Every single piece of your rig ought to go back to the SAME feed.  Use really good power strips if, like me, you have a dozen plugs.  Minimize the "spanning tree".  Put digital stuff (computers, TVs...) on a different circuit, hopefully ont he other side of a power filter. They represent the noise you are worried about and may have, like spies, infiltrated your room directly - dont look too far, the noise is right in front of you.

Use common sense.

I am not an electrician, but if I was building the ultimate system I would use 2 to 4 gauge power wire fitted through conduit. Would it make a difference in sound, who knows. But I like the idea of having everything overbuilt. You can get a 100 feet of 4 gauge from powerwerx for less than $500. If you are going to redo your internal wiring why skimp?