I'm going to buy HID headlights as my next upgrade. I notice that there is two different types of Bi-xenon bulbs. Which is the better bulb, the dual hid bulb or the single hid bulb that moves up and down?? I know that the dual has 4 ballast and the up/down has 2.

 

Personally, I would look for a bi-xenon or a bi-lamp type bulb. These have a xenon low beam & a H3 halogen for the high beam<-- this is what I'm running. The kit is made by Pilot. I think I paid around $150 shipped for mine off of e-bay.