Once you go beyond 6000K, your output becomes worse.
I have 5000k for my headlights and foglights which outputs a bright pure white color
but ideally 4300k or 4500k is the sweet spot if you want the best light output for our reflector housing
In my opinion, I think everyone should consider a projector retrofit since this will actually focuses and utilizes your HID to its fullest potential.
You can find the retrofit DIY here: http://www.solaraguy.com/viewtopic.php?f=20&t=53338
If I were to tackle this project, I would purchase spare headlight housing from your local junkyard for around $30, clean it up, and retrofit them
If you mess up, it's okay since you didn't mess with your original headlights.
It should cost in total around $150
If you don't know the differences between our stock reflectors vs. projectors:
think of it as a flashlight,
Those old flashlights with the filament bulbs and the solar panel looking reflectors resembles what our cars have now
The projectors can be represented as an LED flashlight...
Now if you were in the woods at night, which one would you prefer to use
Hope this helps