I'm a bit confused about MyGig. I wasn't really considering it for my RT until I noticed a story about the options on the new Challenger which said it was available for $850. Does having a MyGig unit necessarily mean it has GPS? Is the unit sold without GPS as a sound system only? The article may have been wrong about the price, but it got my attention because the THX/Nav system in my Lincoln was something like $2500. Is it possible to simply swap out the head unit and get a MyGig with GPS? At what cost in the real world?