From the ad:Horst said:
"While navigating, you can continue listening to the radio, or to your CD changer, if you have one connected."
So it looks like you cannot use the in dash CD while navigating.
"The navigation maps are stored on NAVTECH CDs - one disc (of your choice) is included with your order. (There are nine discs available, each containing a different region of the United States.)"
But it does have two BIG advantages over the HK.
1) It is cheaper.
2) and most important, it is AVAILABLE.