This is true. And I have my sub amp wired to the LOC. I have always just put different subs and sub amps in. I swapped out my door speakers for aftermarket ones but I decided I'm upgrading to a component system for best SQ. The only reason I have not got a aftermarket head unit yet is because I was not sure what all I will neeed aside from the wire harness plug in order to retain some function to my message center. Also I have Sirius satelite radio and I need to find out how to retain that also. How can I go about only adding in the 4 channel amp to my current setup without losing the signal that goes to the rear speaker wires for my LOC. If I cut the wires behind the radio to splice into the door speakers, this will cut off the signal there.