Ahh...that's cool then. I see people putting 80W, 100W, etc. bulbs and I just hope they understand the potential risk of melting wires. Being a firefighter, I've seen my share of car fires caused by people doing things to the wiring in their cars without taking current draw into account. Now, if the XF wiring harness has the wire gauge to handle higer current draw bulbs, the more power to 'em!

For reference:
22 gauge = .92 amps
20 gauge = 1.5 amps
18 gauge = 2.3 amps
16 gauge = 3.7 amps
14 gauge = 5.9 amps
12 gauge = 9.3 amps
10 gauge = 15 amps
8 gauge = 24 amps

Ohm's Law tells you from above that at 12V the factory 55W bulb would need 14 gauge wire (4.58amps). The wires in the XF don't LOOK like 14 gauge, but insulation thickness can deceive the eye. If indeed they are 14 gauge, the maximum safe bulb wattage would be 70.8W (12V * 5.9A). So unless the XF has 12 gauge wiring to the lamps (doubtful), 70W would be the max safe bulb to use on 14 gauge wire.