There are some HIDs that use halogen for hi-beams, but mine are true HID hi/low beams. These do not use two seperate filaments like conventional halogens, these use only a single electrical "arc". IIRC, the hi/low beam "effect" is achieved by the bulb being rocked up or down in its socket by an electrical signal to change the pitch of the beam (I think that's right - someone please correct me if I'm wrong). This is the kit that I ordered:
eBay Motors: Bixenon Conversion Kit Dual-Beams H/L 9008 (H13) 6000K (item 380033285982 end time Feb-25-09 18:04:31 PST)
This is a great kit- completely plug-n-play. Hardest part of my installation was finding a good place to mount the ballasts because the '08 engine bays seem to be much more crowded than previous years.
One piece of advice though (I speak from experience): if you buy this kit, it will include two relays (they're the 2"x2" black plastic boxes with wires hanging out one side). Be SURE to:
a) mount them up high so the wires are hanging down (this is to prevent water from running down the wires into the boxes)
b) silicone the seams of the plastic boxes and make them water-tight!
Mine weren't water-tight and ended up corroding and shorting out. I had to buy another harness, but all has been good since then (knock on wood!).