Terra, it appears that your two outlets are daisy chained, and thus you have in effect only 1 dedicated circuit. That circuit is a perfectly valid dedicated one since it comes directly from a subpanel.
You need to determine the total steady state current draw when all your components are on but not playing music, and then the peak draw when the amp is maxed out. You will use this to help determine if more circuits are needed, and if you need to go to 20 amp. Since you runs are relatively short, that may not be necessary.
I would suggest a minimum of two circuits, although some run several just to be conservative. You might be able to keep the one you have and just add another. Are there any other circuits in that subpanel?
You need to determine the total steady state current draw when all your components are on but not playing music, and then the peak draw when the amp is maxed out. You will use this to help determine if more circuits are needed, and if you need to go to 20 amp. Since you runs are relatively short, that may not be necessary.
I would suggest a minimum of two circuits, although some run several just to be conservative. You might be able to keep the one you have and just add another. Are there any other circuits in that subpanel?