Should Subwoofer Be Plugged Into Same Circuit?

I remember you had a thread asking about power conditioners. Most conditioners limit current and an amp draws the highest current of all your components. That's why typically sources are plugged into the PC and amp is plugged into the wall. With a 20A duplex receptacle, conditioner into one outlet, amp into the other.

Depending on the power of your amp, you may be able to plug everything into the Brickwall. It's supposed to be non-current limiting.

It depends on the total current draw of all your components on a particular circuit. Calculate the total amperage that will be used at one time on the circuit. 
And it's best to use a 20A dedicated line which includes 20A wall receptacle and 20A breaker.

In addition, @almarg correct me if I'm wrong, one of the receptacles needs to be grounded to the service panel, not self grounded. If there are two separate runs of Romex, then both need to be grounded to the panel to help prevent a  ground-loop. This may also lower the noise floor.