I have 100W bulbs in the driving lamps of my truck. They are a lot brighter than the standard 55W, IMO 100W are fine with the law as long as you use them in your highbeams and are respectful and dip them to oncoming traffic.
The ones in the link are H7 Lowbeams in the XF, that may get you in trouble
But IMO the $76 HIDs are the BEST way to go.