I'm thinking about buying a new CTS. I'd like to know if the Navigation System is worth it. I can get the Premium package for about $10,000.00 or buy the same options separately and eliminate the Navigation System and save $1000.00. So, is the Navigation System worth $1000.00? Or, am I missing something? Is there something else that I'd be getting with the Premium Package for that $1000.00 extra?