HID headlight ?'s

[gikken20]

I just got my wife a fully loaded 2007 Yukon 4x4, we love it. The only problem is she has difficulty driving at night. I have HID's on my Jeep but they were done before I bought it. Were getting ready to move from Atlanta to Washington and she wants them for the drive. I've been doing reasearch but there are tons of companies that make them and they range from $60 to however much your willing to spend. From what I've been reading the ballast is the most important part. Also what brightness is the best? I was thinking 8000k Im not sure what is legal and I havent been able to find anything on it. Also I'm gonna call, but does anyone know if it can void my warranty or should i just change them back out if I have to take the truck in? I tried finding some threads but they were for the wrong year trucks, Any help would be appreciated.

Thanks Jake