I bought my 2007 Fusion a couple of week ago, and am beginning to consider things to upgrading my sound system. I haven't fully decided if I'll want to install a new headunit or not. My first question is, does anyone know any specs on the stock headunit? Things that would matter if hooking up external amps, s/n ratio and the such. I have the 6 cd/mp3 unit. Second question, if I were to get a new headunit, how can I keep the stock aux input in the console? I've seen people talking about the pie adapters, but that seems geared to adding a new input. If I were to go from the jack in the console and follow it back toward the headunit, what would I find on the other side? Or could I just get a headunit with a rear aux input and run a new cable to the spot in the console and make it fit? My last question is, what do I need to look for in a headunit in order to be able to keep the steering wheel controls? Is that a feature of the headunit, or the wiring harness? Thanks for all help! I always like to do my research and try to know what I'm getting into before starting any project.