Wow this is one mega topic.
Lucky so many knowledgeable people who have already made a dedicated room.
Vic for your ease it would be best to make sure each outlet in the room is separate to avoid grounding issues. 120V./20A. is sufficient for AVR/Amps high power items. Though 15A. is typically enough. I would Put the 20A. only on the lines you may use or intend to use for main sources.
One detail is the items will only draw so much power anyhow. Extra on tap is good though most items will not need it as they can't draw any more than they are designed to.
