I'm doing this myself, I lucked out and RTS gave me the cyber monday deal up till last friday so this kit (listed below) cost just $200ish. The kit thats a direct fit with the 05-07s (after you bake open the lights) is the H1.
This thread gives the same concept idea of how to do it. He had some of the parts I think but you'll need the bulbs, ballasts, shrouds, projectors and from what Andrew at RTS told me, they throw in a CANBUS compatible relay which knocks out any possible light-out error and also stops the flicker. The Morimoto ballasts that are included are very good quality. Also, you'll want some butyl resealing tape ($10).
FYI you'll want the 9006 for your lows (these are Bi-xenon) by the way. That means that there's a pigtail clamp you simply clip into your highbeams so that when you hit your high beams you retain the halogen lamp for "flashing" but if you're turning the high beams on the HIDs will activate a solenoid which then changes the HID pattern to a high beam (so you'll have four lights on) and then back to the two HIDs when the highs are turned off.
Alternatively you can go with what the DIY thread did and just get the low beams and make your own kit. Personally I liked the idea of the bi-xenon (some people go a step further and set up quad bi-xenon for 4 low and 4 high beams at all times.)
As noted in various threads you must specify the GATLING shrouds for proper fit and make sure theyre the shrouds with FOUR screw holes in the back.
DIY: [Guide] WK H1 Mini Morimoto Retrofitting Low Beam
Complete Bi-Xenon kit
Or you can get the elite kit and buy the H1 projectors separate: