I've got the 6,000K Xenon HID's in my low beams only and love them. For me it was simply an issue of being able to see at night. Regardless of legal issues with conversion kits, once you've experienced driving with the HID's you just can't go back to any other (filament) lamp. The Crossfire uses a reflector in the headlight so just be sure the lights are aimed properly and there should be no problem.

By the way, the Sylvania Silverstar lamps are a complete joke. Don't waste you $$ on them.