What is the best way to add nav to a 2008 GT with a Shaker 500 system? I am thinking about adding nav and I am trying to find out what my options are. I asked a guy at CarToys and he was saying I would need to have all the wiring replaced. Is this true? Is there an alternative? What nav units will work best with the existing Shaker 500 setup? I currently have Sirius installed too, but I never used it enough to justify the subscription cost so that is currently unused. I want to also get iPod connectivity and was originally looking at just adding that, but if I am going to change things I should go with the nav initially. Any suggestions on the best approach, best unit etc? I am hoping to stay around the $1000 mark but a little more is OK.