Is it possible to get a line in to a standard 172 Cup head unit? Was thinking of getting a personal MP3 player and it would be nice if I could run a wire from it into the standard stereo. Ive seen these FM transmitters that are powered from the cigarette lighter and broadcast a signal to a free FM channel...but I doubt theyre very good and have seen mixed reviews. Anyone seen a solution for this? (I was thinking along the lines of the CD changer input - if theres no CD changer in the car is there a socket on the back of the HU that could be used?)