I have the 6000k HID kit on my M3 and its got beautiful light ouput. The 4300k still has a little yellow in it. Here is a good link for light comparisons http://www.geocities.com/kitwetzler/ Below is a picture showing the difference between 6000k and 4300k. If it comes up as just a red x, right click on it and click show picture. Geocities has issues.




You can see how blue the 6000K kit is on the left. It's very nice. I was surprised at how much I liked it. This VERY high quality (and expensive) 6000K HID kit puts out as much light as a 4300K kit, as obvious by the light. However, this is not always the case. Many 6000K kits put out much less than comparable 4300K kits. The ZKW lights also put out a sharper kick up on the right side, the bosch projectors are more diffuse after they kick up.