Dedicated power....

Depending on the type of amplification you are using a 20 amp circuit may or may not make a difference. As far as using high quality outlets go they can help and certainly can not hurt. I believe a good quality hospital grade outlet is fine but others will differ with me.......so to each his own. I personnally use PS Audio Power Ports and I am very happy with their performance. And I figured I went through the trouble to run the circuits I might as well go a step further and buy the better outlets.

It won't make any difference unless you change the size of the Romex back to the breaker panel.

Typically per NEC:

12 gauge wiring for a 20 amp max breaker
14 gauge wiring for a 15 amp max breaker

And to add to what Forrestc writes:

If you're going more than 15 or 20 feet from your panel, go up another wire size to make up for voltage over the distance.

20A = 10ga.
15A = 12ga.

Are changing the outlets easy.

For changing the outlets, all you need to do is unscrew the receptacle from the electrical box, and then unscrew the wires from the receptacle. As the wires are stiff, you should have a pair of pliers to bend the tip of the wire to replace it around the screws of the new receptacle. Make sure that the individual wires in the Romex (a black hot wire, a white neutral wire and a bare ground wire)are attached to the correct screw in the receptacle. (When you remove the old receptacle, note which wire is connected to which screw.) It takes all of five minutes.

And for God's sake, make sure the power is off!

And when you check that the power is off, check BOTH plug outlets in the receptacle. You could have a split duplex receptacle. In other words, each plug outlet could be powered separately with its own wire. You need to turn off two breakers for a split duplex.

Sorry, the sentance should read "to make up for the voltage LOSS over the distance"
.

Sounds easy..

Spaz
The screw terminals on the receptacles are color coded.
Green is Ground or the bare wire,Brass color screw is the hot or black wire and silver color screw is the neutral or white wire.Sometimes and depending on the wiring in the wall the hot wire will be a different color such as red or blue but the neutral is ALWAYS the white.Before you do any work shut off the breakers or better yet do what I do and shut off the mains for whole house.It helps to work with a flashlight .
Best
George