Dedicated 20 amp circuit. 10/2 or 10/3?

Eliminating noise/hum

I have three dedicated circuits to my audio area and all three are on breakers next to each other on the same side of the panel. 

Since this wasn't mentioned; this means that 2 of these circuits are probably on one 120 volt leg of a 240 volt service, and the other circuit is another another leg. 

Thinking many of you are not in US, with mention of 220v/240v, I’m located in US … I have been planning, in process of redoing, movie/listening location with a single 20A/120V for three amplifiers (MC303; MC152; Mi254) and two subwoofers (JL F113) … You guys got me all worried thinking that one dedicated 20 amp is not enough. I don’t know how many people notice that most power conditioners, Panamax/McIntosh MPC500 max out at 15A …

Are you all plugging into outlets directly with your components? McIntosh MPC1500 is 20A …

maybe in my case it would be better if I bought two MPC500s used one for regular amplifiers and second one for the two subs? This way, I could justify wiring two different “dedicated” circuits (beyond normal plugs) into the room.

Oh, in the US, 12/2 for 20A regardless of 120V or 240V.