What size power adaptor for a games console in the car

[fiatpower]

I am driving to France to watch the Euros with some of my mates. To prevent them getting too bored I have borrowed a portable dvd player with two screens (Centurion DVA-320S2) and want to hook a games console up to it (I used to hook a PS2 up to it when I was younger). The power consumption of the dvd player is 15w according to the product specs in the manual. I have to have the unit running to power the screens. The car in question is a 2007 Ford Focus mk2 with 1 12v power socket in the front. I have read that there is wiring for a 2nd socket in the wiring loom in the boot (designed for the estate version) however I would have to wire this in myself if I need it.

Few questions:

Would an Xbox 360 be too powerful to run in the car? What size power adaptor would I need to run this if not? Can it run off the 12V socket or does it need to be wired directly to the battery?

If the Xbox 360 is too powerful I will use a PS2. What size adaptor would be needed for that?

As I only have 1 power socket currently can I use a power socket splitter to plug in the dvd player and the power adaptor for the games console or would this be too much for the 1 power socket? If I can't do this I will have to wire a new one into the boot.