Jaguar brand is always special for luxury cars. And they have relased to new cars to the market which can name it as ultra luxury cars. Those are XK and XKR car models. The XK model is first produced in year 1997 and has been revised for year 2007.
Engine comes as the major difference inbetween XK & XKR. Though it has a same kind of V8 engine, XKR has an addtionaly supercharger because of that Jaguar XKR can generate 420 horse power while Jaguar XK generates 300 horse power. Both cars have same 250 km/h speed limit.
And another thing is Jaguar XK has a saftey sensor. It will raise the hood of the car if the car is in unsaftey situations.
Engine 
Type :
supercharged V8
Power
300 hp (XK);
420 hp (XKR)
Performance
Acceleration:
0-100 km/hin 6.2 sec.(XK);
0-100 km/h in 5.1 sec. (XKR)
Top speed :
250 km/h
