I did a quick search and to no avail did i find anything. SOrry if its there already but quick question. I have a 2010 Ford Expedition XLT with 6 cd changer and sync. Now i wanted to put in an oem nav. I was wondering what else do i need for it to work beside the amp. Becuase i see 4 ports on the back of the unit, but i only have two. Was assuming one if for the subwoofer which i dont have.