Which "K" for my MH bulbs?

[MikeP]

I'm going to buy some MH bulbs for the 190g reef I'm setting up. My ballasts will run 175 watts and I have two. I know that is not quite enough wattage but I will add more lights when I get things going. Right now I need to know what "k" I should go with. I can choose between 14000k and 20000k, the prices of the bulbs are the same. Which should I order?

Thanks