I just bought an AVH-P4000 and thanks to the tips on this site, I can now "listen" to a DVD while driving and my passengers can watch.
I used a 4-pole Auto Relay from Radio Shack (Part#275-226, no 87a, just 85, 86, 87 & 30) and I followed the instructions and picture from this sight.
Works like a charm with no switches to mess with...
Thanks a million to all