Just to clear up some questions and put some facts out there...
There are
halogen projectors and
HID projectors. Halogen projectors do not have the proper cutoff shield necessary to put HID's behind them, they are manufactured to focus halogen light in a different pattern than HID lighting. So, be aware that it is possible to have projectors but not have the proper cutoff shield within the projector for HID's.
Also, note that it is possible to have "proper" HID lighting with a reflector housing and not a projector. Cars such as the Toyota Prius come stock with HID lighting without a projector. How is this? The bulbs are different. A HID bulb for a reflector housing will have a type of shielding around it, creating the proper cutoff (thus no need for the projector and cutoff shield). For example, Philips manufactures both kinds of HID bulbs. Their HID bulb meant to be used with a projector will be denoted D2
S.
http://www.kbcarstuff.com/photos/PB-D2S-4K-2T.jpg
However, their bulb meant to be used with a reflector housing will be denoted D2
R.
http://www.kbcarstuff.com/photos/PB-D2R-4K-2T.jpg
Notice the difference between the two. The D2R bulb has a shielding built around it to prevent light from spraying up away from the road. Note that while this does act as a shield, it is not nearly as crisp of a cutoff as can be achieved by using a projector and cutoff shield, but it still remains a MUCH better option than using nothing at all.
Also, 4300k is the brightest light possible for HID's. If you want the maximum output, go with those. 6000k tends to be a bit blue. However, I have found that 5000k kits are the perfect compromise. They are just a slight hint of blue but don't attract unnecessary attention due to it.
You get what you pay for in HID kits in the quality of the parts and the warranty. Many people get away with using cheap kits, many do not. It's a crap shoot, at best, if you're going for a budget kit.