Single dedicated line query

At first I went with two dedicated lines from the panel.
One was connected to a 20 amp fuse(source components)the second was from a 30 amp breaker for the amps.

I have since gone to one dedictaed line from the 30 amp breaker using 4 wire Romex 10 guage into a Shunyata dual receptacle which feeds power to a Hydra 2 for the power amps and to a Guardian 2 for the source.

There is absolute silence , except when the music is playing.
There is no power line buzz, hash or hiss,or hum, just a noiseless background.

It wasn't this way with two lines.

Very good,that's why I had my electrician do mine.
No worries,DONE.

Your electrician will tell you that the correct wire size is 12ga. with a 20 amp circuit breaker.
02-03-10: Dobieguy

#12 awg is the bare minimum size wire per NEC for a 20 amp branch circuit.

It's not possible to expect to get 6 or 8ga. wire into a wall outlet box and then hook an outlet to it.
02-03-10: Dobieguy

Most 20 amp branch circuit breakers made in recent years will accept a max wire size of #8 awg. Receptacles, usually #10 awg copper max.

What you "suspect" should be used is one thing,the electrical code says what is the correct thing to use.
02-03-10: Dobieguy

NEC code is a bare minimum electrical safety code......

Article 90
Introduction

90.1 Purpose.

(A) Practical Safeguarding. The purpose of this code is the practical safeguarding of persons and property from hazards arising from the use of electricity.

(B) Adequacy. This code contains provisions that are considered necessary for safety. Compliance therewith and proper maintenance results in an installation that essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use.

(C) Intention. This code is not intended as a design specification or an instruction manual for untrained persons.

NEC 2008
NFPA 70
.

I went2X40a breakers+7AWG from my main panel to the livingroom and their put a SUBPANEL(with 8X15a breakers.Wiring in the subpanel is 10AWG+ wire to the receptacles is 10AWG.so that gave me 16 outlets.Electricians don't like 10AWG as it is hard to work with.
I don't want to restrict power to my amps so if 10AWG is probably better then I'll do it,I definately want to be sure were not starved for power as alot of audio folks +pros go the 10AWG route and some do the 12AWG.My mind is at ease knowing from the panel to my gear I have no power issues.Of course with a couple of Torus(s)up front I get more power in reserve than the wall can give me,but that's another story.

Your electrician will tell you that the correct wire size is 12ga. with a 20 amp circuit breaker.
It's not possible to expect to get 6 or 8ga. wire into a wall outlet box and then hook an outlet to it.
What you "suspect" should be used is one thing,the electrical code says what is the correct thing to use.
Also every time splices are made,wire sizes changed and pigtails used you are defeating the idea of a dedicated line. A saying in the trade says it all:
WIRING IS NOT A HOBBY. GET A PRO!