More than likely, that lift will offer around 2" of total lift. It appears to have the same rear spacer as the Rough Country lift, and the strut fork won't lift as high as a top mounted spacer will. If it does lift the full 3", you'll start having problems with your front end geometry.
That being said, it'll probably level the XK out. But for the money, I'd recommend going with the more tried and true Rough Country lift, or the Crown Automotive variant I've posted about. It'll offer similar lift, and be cheaper.
2006 XK Limited, Hemi, QDII
245/70R17 General Grabber AT2s
Superchips Flashpaq 3872, Ported/Polished Throttle Body, Crown 2" Lift