Very informative read on HIDs, and the truth why anything higher than 4300k is useless. I'm glad I found this.
http://www.intellexual.net/hid.html
xenondepot.com sells genuine Philips bulbs, thus is why he (Steve) only lists 4300k for that brand. Anything on ebay that lists "Genuine Philips 6000k or 8000k" bulbs is a scam. Philips or Osram-Sylvania only make 4100-4300k. Period.
Beware! :)