I have been shopping for a car for a while now. What I have been waiting for have been incentives. This weekend, GM is offerring an excellent incentive; free money. Zero Percent financing. That has pushed me off of my indecisive fence of CTS vs. certified convertible BMW vs. certified Audi convertible. There are no great rates (3.9 for BMW) for the others. I found the color I want, White Diamond. I can live with the interior gray/ebony, it has the heated seats which are almost essential BUT there are no CTSs with nav and a 6 CD changer. How does an after market in the truck CD changer work? I know I can get a multi cd unit. How does it operate inside the car? I am giving up a 4 CD changer in my 300M. Also, what about the nav stuff? Where does the unit that you can buy fit in the car? I could get a 2007 CTS but I miss out on the free money and for what? Toys? I don't go that far that I 'NEED' a nav system. Its a toy.