I have an Alpine headunit in my Mustang with the iPod interface and its awesome! I also have the Griffin iTrip FM transmitter thing that I use in the Jeep and when i am driving trucks at work. sound quality is major :tdown: and it only works sometimes (found out some tricks to get it to be more reliable), but despite the downsides, its nice for my application. the aftermarket headunit/interface option is by far the best way to go IMO. correct me if i am wrong, but i do not believe i see where you posted what kind of mp3 player it is, so this may limit your options.