DDM slim ballast 4500k with the 9007 (hi/lo) bulb is what I'm running. I like the slim ballast versus the regular size because the slim ones are easier to hide, and don't produce that noticeable of a hum sound when you turn the HID's on. As for temp. I'd stay in the 4500-6000k range anything else and your gonna have cops all over you at night due to the very noticeable brightness and color of your lights.