Mine has some pioneer unit in, plays dvds has lots of connectivity, but its a few years old now so has most likely been updated into something better.
Depends what you want out of it, do you want....
lots of gadgets, app conectivity, camera input and stuff. (maybe something cheap of ebay)
does it need to connect to an amp and need lots of pre-outs (needs some shopping around)
does it need to sound awesome and the rest of it is add ons (well known names are normally your best bet)
Hope this helps a bit :)
(woop go 2003 blobs ! here is my Double Din unit)