Hey i was jus wondering if the serial code of the indash dvd player for example "AVH 6500" has to match the "brain"(processor) serial code in order to work

 

no, pioneer doesn't need to match by serial number between the brain and the flip out but it is important that pioneer didn't make any major changes between those two model years. if it looks the same on the outside (plugs, etc) as the older one you shold be fine. I have switched up several of alpine, panasonic, pyle, and pioneer brains, some for repair replacements, some for upgrades to 5.1 sound.