Late entry into this discussion, but here's my experience.
The ebay "projector housings" that replace your stock housings are all crap. They just suspend a projector-like lens piece in an otherwise regular reflector-type housing. If you examine a real projector assembly, the lens is affixed onto a housing which incorporates the cut-off shield and a parabolic bowl which focuses all light output into the lens.
Anyway, I've been down that road, and have tried so many different HID setups it's rediculous, and here's my current work in progress:
Bosch bi-xenon projector with real Phililps XenDrive. OEM from a Volvo S60. Pics taken with cell phone, but you get the idea. After you use OEM hid housings, you realize that everything else pales in comparison.
BTW, I also have a Philips kit with an H7 base in my Mercedes OEM housing, and it looks like junk compared to my Supra.
-Ray