What wattage are you using? When I ran halides I liked the Phoenix 250watt 14k bulb but the 150watt put off a totally different color. The best bulb I ever ran was the Aqualine AB 13k bulb. My sps seemed to really respond to it. They are expensive, though they seem to have come down in price in the last few years. I used to have to pay around $115 for them.