I have a 2011 Silverado 2500HD LT, it has on-star and CD, mp3 player with Sat radio. I like how directions show on the LCD of the stereo when using on-star. but I would like to at some point upgrade to an aftermarket stereo. but if I do that I don't want to get one that loses this capability. is there one of those touchscreen nav stereo systems that will work with my current features while giving me the new ones? basically still have the onstar sourced directions still show on screen if I don't use its built in nav? I would like to have another nav system I can operate inside the truck without calling onstar. What I really like about the onstar is I can send the directions to my truck via my phone or ipad.