The highest I would go is 6k, its what I have on my bike. It has that light blue look, but still maintains a nice reflection on the road. Anything else (I think) you'll wish you didn't. Most people without projectors just "think" it's brighter because the light is blinding the fark out everyone.

Just look at the Kelvin chart, and go with the temp that produces a blue light but nothing too excessive.


This will explain about the color tempature
http://www.hid-online.com/hidonline/...colourtemp.htm