Do not get a pop out dvd/nav player, that'll just look tacky and ricer-ish. If you're going aftermarket you have to go DD size and you might as well fill it in with a DD head unit. To do that, you can get the DD dash kit, but you also have to change out your climate controls because with OEM, the radio and climate controls are on the same circuit board.
A sweet setup would be a nice DD HU (either go Pioneer or Alpine IMO, both offer a DD HU that will sit flush) in the dash with a custom screen setup where the OEM one would be and an outboard nav system where the OEM would be with RCA converters to plug into the custom monitor.
Looks like you could save probably max $1000. Here's the websites for everything.
Dash kit http://www.grubbsperformance.c....html
Custom monitor setup
http://store.mp3car.com/category_s/53.htm
HU and outboard nav
http://www.crutchfield.com/S-X...enu_3