I am using one 400 watt 4300k which is obviously too yellow. (bulbs came w/) I added 1 40 watt blue actinic and 1 50/50 blue/sunlight. This is still too yellow but is sufficient light for decent growth.
If you are ever in a pinch for a bulb, Home depot sells the 4300k bulbs for $29.00
I would hate to buy an expensive bulb only to find I didn't like it.
Anybody got any used MH bulbs to sell cheap?