I want to do this safely!one objection to using a socket circuit in the the ceiling, is that, unless you are in a bungalow, it is pretty sure to be the circuit that feeds the upstairs sockets. So an innocent person might turn off the ground floor socket circuit, and work on your speaker socket, expecting it to be dead.
A good electrician is supposed to be wary of such things and test every time, but it is a mistake many people have made, once.