The Xenon head lamps are projector lenses that reject upward light into on coming cars. Because a halogen bulb isn't anywhere near as bright a bog standard reflector head light doesn't cause too much grief to on coming cars. Stick a HID kit in and you'll soon be blinding lots of people.
I've been there, done it, had the tug, not worth the agro!
Get the proper lenses, at that price I would bite their hands off for them!