NAV makes no difference for the connections in an X3 - they're all located in the same area and the same radio is used in both applications (split radio/nav system). DICE is the better of the two kits, Dension has has reliability issues and has since pulled out of the states.
Here's the DICE kit you need:
DICE iPod Integration Kit for BMW (Trunk Interface)
http://www.europeanautosource.com/pr...roducts_id=268
If you need the DICE, we ship to anywhere in the world and even a few people in Spain are running our kits: