4300K is factory xenon temps, and is the same colour as daylight.
Any higher and you get glare and it will strain your eyes.
The bluer it is the more your eyes will be strained.
I am of the opinion that xenon technology is there to improve your night vision. The 'blue' xenons don't actually 'help' in the long run, but are a hindrance to your night driving.
But hey, knock yourself out with your 8500K lights... you'll be more likely to risk a defect too.
I'm going to retro fit factory 4300K projectors and globes to my 32 rather than a plug-in globe replacement, to ensure I get the right light pattern and cut-off light lines. Pics when i get around to it...