depends on if you have the GT which already has HID in it or the sport and will need the entire kit and ballasts.
I have the sport which has H7 so I needed the whole kit. I bout an 8000K from my favorite seller off EBAY and paid $62 shipped for the whole kit. Still working and looking great! 6000K will be brighter tho, but the 8000K gives a nice blue effect to it. Good luck!