Heres what I'm thinking:

I already have an Alpine 9813

I might get an Alpine DHA S680 (6 disc dvd changer) and the screen by mattjk off ebay:

I could put the 9813 in the spot where the factory clock is, put the screen as shown in the pictures, and mount the changer under the passenger seat / glove box / back of the wagon.

The twist on this is, I'm getting new components first and I'm thinking about running them off the front and rear channels of the deck (its an option to run the tweeters off the front channel, the mids off the rear). So what happens when I play a DVD? I'm guessing the deck knows its only outputing 2 channel stereo instead of 4 channel and the dvd sound will come out accordingly right? It wont send the front channel to the tweeters and the rear channels to the mids would it?