Dedicated Line for my home theatre newbie


I see lots of threads but want to double check with all the folks on here for help with my idea to put a dedicated line in. So, I have a simple system that consists of a 55" Plasma, NAD Reciever, Denon DVD-2910 and Monster HTS-3600. The room is directly above the garage which is going to be finished off later this month. Before I get the insulation, drywall up I wanted to run a dedicated line from the main panel to my media room directly above. I was thinking of Romex 10/2 wire but the electrician is saying that is too big for my panel and he suggests 12/2. Does this sound right? Or is he just being lazy because it maybe harder to work with? Planning on using a PS Audio outlet that says it can accept either 12A or 15a. I might go ahead and grab a hubbell Hospital grade that folks here say are good bang for the money. Trying to keep costs down. Let me know your thoughts. Thanks.
hricikda
Ok, I'm a dummy. I realized that I hooked up the system minus the subwoofer to the new line. I came home last night I unplugged the sub and plugged it in the new line and the noise went away.

Update on the system: My wife and I were watching her show :) American Idol and she even commented on how it sounded more in your face and clearer. There were a few occasions that we heard sounds that we though were our dog playing with his bone when in fact it was people in the background in the audience. Pretty amazing what a dedicated line can do. I'm a believer....Plus, it only cost me $60 for 3 dedicated lines plus materials.