I have Diode Dynamics' HID kit. IMHO, 5k is the best; 6k being a bit too much.
http://www.diodedynamics.com/store/l...conversion-kit
While people do recommend going full retrofit, I simply bent the metal "squirrel finder" tab inside the stock projectors to prevent blinding oncoming traffic. I haven't gotten any flashes or pulled over from law enforcement so far, been installed for almost 6 months now.