If your set on metal halides you be looking for a bulb more in the range of 14-15K depending on the brand. 20k is more blue, and 10k while sometimes white, can also move to yellow over time.
I can't really recommend much, but I use an XM 15K bulb supplimented with two actinic bulbs. You can look at my lighting, but ignore the horrid algae outbreat at
www.marineatomica.com under Journal.