If you allow one light per a 2'x2' area, you can't go wrong. I think you could run a 14k bulb without actinics just fine, as you could with some of the 10k's (just check the Kelvin ratings first). With 250w MH, you can keep any light loving corals you want up to a tank depth of about 24". Double ended fixtures are definely the way to go if you want the most "bang for your buck". They are not that much more expensive, and give the most intense light. In fact, with some bulb, reflector combos, the intensity rivals 400w single ended bulbs!