5k range will be the best light output and also brightest as mentioned in the posts above ... this has the added bonus of the "color band" created by the projector being much more visible ... projector headlamps create a bright colorful band of light where they cutoff on the area they are lighting ... this is highly desirable in the light guru circles, where as the colorful 8,000/10,000/12,000k bulbs are largely seen as "for show only" ...

but get what you like we all like a little show with our go.