i personally would not go any higher than 6000k no matter what type of headlight you have.
6000k is quite blue with some white behind it.
5000k is about an even ballance of blue and white
4300k is stock HID colour (white)
3000k is yellow
8000K = looks good but very limited / poor functionality
10000k = well your just gay (no functionality, just 'looks')
12000k = purple is not cool (no functionality, just 'look')