ok, there are a lot of misconceptions that i REALLY need to clear them up.
first, i would strongly suggest against getting anything but philips or osram bulbs, specially when you get higher color temperature bulbs like the 6000K. these bulbs are not easy to make, and there is a reason to invest more money on the better brand ones. the philips and osram will last longer. korean brands like K2 and Hela, they both have HID bulbs, but I haven't heard good stuff about them at all. Moreover, with those brands, color temperature tends to vary more, so you might get one that's not as white or one that's dimmer, etc... so pleeeeease, get philips or osram....
and about the 8000K bulbs..... imho, it's stupid for anyone to get them, coz' they are not nearly as bright and they attract no one except cops. keep in mind, you are dealing with color temperature NOT the actual temperature here. they are two very very different entity. i mean if your bulbs are running at 8000K temperature, you'd better start running before your car catches fire.
color temperature is a standard way to describe light color. 4100K, which is what our stock hids are rated, are actually the natural color of the sunlight. it gives out the MOST light and it's actually the brightest. anything with color temperature higher than that are actually getting less and less bright.
for example, the 6000K bulbs, they are actually around 20% DIMMER than the 4100K. however since the light are much whiter, you don't feel that it's dimmer. and in fact, i believe 6000K is the color for the white? anything more than 6000K is getting bluer and bluer. I believe at 7500K it's more like green, at 8000K it's like blue, and at 9000K it's more like purple.
8000K bulbs are actually available already for quite some time, however you will need to get new ballasts for the bulbs. our stock ballasts can't ignite those bulbs. but like i said, 8000K are actually MUCH MUCH dimmer than the stock ones, and above all, they are so blue that if there is cop across the street, they would take pleasure in making a u turn to pull you over. so why get a blue bulbs that's actually dimmer?
so imho, 6000K is the limit and that's what everyone should get. anything higher than that i wouldn't recommend at all. try to search for pics on the 8000K bulbs on the internet or get to see one yourself. i saw some already (7500K and 8000K) and i am disappointed.