I've been wanting to install a headphone jack outlet to the back seats so that if a headphone were inserted into the jacks, the sound from the main speakers would be turned off and the sound would be going directly thru to the headphones. I realize I will probably need a to step down the power from the speakers to the jacks, but how to rig it so that it will cut off the power to the main speakers is the question. I'm thinking 3 headphone jacks will be installed... Anyone have any suggestions?