ross i had my kenwood dvd player in my last car, it was a 7" touch screen with mp3 compatibility and it was fantaistic, but......
what you have got to remember is that the player will have to scan the disc every time you start your car,
now with an mp3 cd thats the equivelant of 800mb when full which takes around a minute or so, but with an mp3 dvd thats 4gb when full, now that takes around 5min+ just to scan the disc before you can listen to or even search for your favourite track
my car does not even run for that long on some journeys!
my advise would be to stick to cd mp3, or go with the touch screen tv but try and get a carputor or hard drive to store the music for instant access. trust me it will pi55 you off after a short while.
i ended up buying a 10 disc MP3 cd changer to go with the headunit and that was more than suffice
on a different note, is the recess for the stereo not be a problem for the flip out screen? i still have stereo but have read alot about them not fitting so havent bothered trying.