If you must know, the only way I see you doing this legally is to install an electrical box at the connection point on the units. That is, you have to mount the box in the back of your gear so that all live parts are inside the box. Not only that but the wiring to the units have to be in conduit all the way to the box.
Second, you need a switch near each component so that you can be sure that they are disconnected (this is what we call a safety issue) or you can use the circuit breaker but it has to be capable of being locked in the open position and in plain sight of the equipment. If the units are less than 300 watts, you need not worry about this detail.
Lastly, I got to say that what you have planned is highly unusual and not recommended by any local code official, the NEC or the NFPA. Best of luck and check the battteries in your smoke detectors.