
You could probably do this directly to the cord from the speakers since you clearly aren't worried about voiding any waranties or anything. This is pretty easy to do, doesn't take long, and even gives you an easy on/off button that actually shuts off every part of the system rather than the way many on/off switches on many systems seem to leave parts (such as the amp) powered and while they basically aren't doing much, they still do enough to grow a little warm and probably cut into the total lifetime somewhat. If it's backwards and you cut the ground instead of hot wire you may have a little trickle from time to time and a zap or two, lol. The ground wire should produce no voltage when testing it against the mains ground and the hot wire should produce voltage when testing. Don't trust electricians to have always gotten it right. I've seen more than a few bad screwups in one house alone even.
