BMW's, Merc's and traffic police Vauxhalls and Volvos actually use 5000k,
Osram Xenarc Cool Blue Intense bulbs. But these are genuine quality parts, and proper fitment designed to take Xenon bulbs (D1S, D1R, D2S, D2R) - not your cheap chinese copies.
I personally had 8000k, but they looked too blue (crap) for me, so changed them for 6000k which looks pretty good and gives twice as much light on the road than shitty halogens.
Which ever you choose, make sure you get angels or projector morettes to go with them, otherwise they will look cheap and nasty, and not give you the rainbow spectrum of deep blue and purple cut off when you look below the beam.
Whoever says Xenon lights don't light up the road as much as halogens clearly doesn't have them! Driving with properly adjusted xenon lights
with projector lens, I would say gives me at least double the vision - and that is not because they are blinding everyone (just passed the MOT headlight alignment the other day) - they reflect cat's eyes (or real eyes) far better. I do alot of night driving and I wouldn't own a car that had halogens.
I find it better to run the main beam wired so they come on together, not as original that the dipped beam would turn off with the full beam on.