Sorry for bringing up a dead thread yet again, but this is exactly what I am trying to do. I have a 2012 Galant with the Rockford amp/speakers and the mmcs system. I'm trying to install a Pioneer 4200NEX and would like to keep the steering wheel controls. Can you send me the wiring diagram on how you have this setup? If I understand correctly you got steering wheel controls working and the stereo is using your rockford amp?