I just got my new 05 Z about two months ago, however I didnt pick the model with the Nav system. Now that I see how vital it is I am going aftermarket. I have chosen the pioneer system. The motherboard of the Nav and the DVD will go under the passenger seat and their is a 6.5" screen that is going where the normal stock Nav should be. What do you guys think... It is costing around $1,700 which includes the installation.