The wattage kinda determines how bright they are. A 55w HID kit will have a more powerful light output then a 35w HID kit. This being said... with a 55w kit, you will lose some of your color from the bulb. More white will show through then blue.
and if you liked 6000K, you'd probably be disappointed with the 12000K. It's very blue. Also when you travel higher in the color temperature, you lose light output. So you'd see a lot more road with 6000K then you would with 12000K.
My personal opinion is that I hate blinding blue HID's. I mean 8000K is more then enough blue, but hey it's up to you. Hopefully this helped a bit
