You could get a navi sysytem for about $1300 and buy a 7" screen to fit in the double din. Then put your radio in that tray that attaches to the bottom of the opening under the radio.
A monitor like this would fit nice:
http://www.millionbuy.com/fart7000mhr.html
Here is a 7" screen in the dash:
http://www.v6performance.net/gallery...cat=500&page=1
And here is scree w/that piece I was talking about:
http://www.v6performance.net/gallery...cat=500&page=2
Or maybe something like this:
http://www.sbhcorp.com/scripts/homeViewItem-944.html