I would very much like to hide away the amplifier and somehow have its
power controlled by the presence of a line-level signal (this is for a
home system). In a car this is accomplished with the 'relay' line
that switches the amps on when the head unit is turned on. I would
like the same effect for my home system that switches on and off with
the presence of a line-level signal and of course an adjustable delay
before switching off. I don't have any 'switchable' plugs to plug the
amp into. Any suggestions?

thanks,
Sean