Needing to isolate the 2 stereo amps from the battery when not in use do to them draining down my battery, even with no trigger wire signal, and don't want to constantly be switching a dedicated battery switch. I was thinking of using a 40A or so automotive relay to make/break the 12V power cable using the head units turn on lead to signal teh relay. A car stereo shop suggested a starter solenoid since it is more HD. Not sure about that thinking the solenoid isn't designed to be held closed for an extended amount of time, hense my thinking a relay is best. Can the HU's turn on lead support a relay or solenoid current draw to activate?