Between the 5K and 6K light illumination, you will NOT really notice any difference
dude, people might tell you there's difference, and there MAY be, but I ride with
a buddy who rides an '05 Giggy 1000 with the HID 5K and I got the 6K in my Hayabusa.
IMHO there is no real difference beside the color. It's deceptive.
So I personally like the blue hue of the 6K better because it's got that luxury look.
I got mine from
www.xenonking.com because they had some kind of discount going
for Hayabusa.org members 3 years ago.
I bought the same McCullough kit for my GMC Jimmy Diamond Ed and I have
had 2 ballast ignitor replacements on it, obviously it see's more usage
but they were both replaced under warranty. No problem, so they are a good
company to deal with IMHO>