While I haven't swapped it over to the XJ yet, I ran a Kenwood DNX-5120 in my mazda3 for about 2 years. I'd rate this unit 8.5/10... The menus are not great, some of the touch buttons are in weird spots, and it takes about 20 seconds to 'boot' up. However, DVD and audio playback are superb, and the built in Garmin GPS (basically a built in nuvi with a 6.5" screen) is absolutly fantastic. My wife and I would literally leave the house to go out to dinner, get lost, then make the gps find us a restaurant, and then get us home. I'd buy it again just for the GPS....
I bought this one new for 650 a few years ago, you could probably find it on ebay for ~500...