I know I'm bringing to life an older thread here, but did you go with the 8500 and 250? How is it working out for you so far? I'm looking to upgrade as well and I'm wanting to retain every factory function I've got (BOSE, 2nd row entertainment, back-up camera and sensors, bluetooth, sirius, onstar, door chimes, etc.). I use an iPhone 5 now as well. Did you go with the Pac-Audio RadioPro 5 (RP5GM31) interface kit or the Axxess (ADGM100) interface or even something different?