Check out my experience in construction last year in the PSA threads; do a search. Ted Smith and many others had great advice.
For starters 10 gauge, Solid wire is the most recommended gauge and should not cost much more than 12. My total installation from the main panel to wall socket behind my system was less than $800. Adding a second line at the same time should save labor. See Ted’s suggestion, one line for Digital and one for analog. Both should be well grounded and have their own rocker. Regarding grounding, have your electrician check your house grounding. Since I don’t have a turntable, i.e. play vinyl I stuck with one line.
Once installed, I noticed little improvement on sound quality and clarity. I live outside a small town and believe incoming AC to my house was ‘cleaner’ that of a city. And wiring in my house seems clean, I am fortunate.
I later added a re generator which had an immediate and huge impact on sound quality. But I am glad I installed the 20 Amp circuit first. I think that is the right order to appreciating your system improvements as you add them.
[edited on 9/12 to remove incorrect statement about gauge spec]