Which "K" for my MH bulbs?

[muck]

10K would be a nice crisp white look, 20k would have more of a bluer look to it and 14k would be a combination of both. Of course this varies with bulb manufactures as some 10k bulbs can look very yellow and some 20k bulbs can look more like a 14k.

10k bulbs also generally put out more Par (Photosynthetically Available Radiation) and a 20k bulb less Par. The more par your lights put out the more available for your corals to use. The more available the better the growth and color (also dependant on a host of other variables).

I'll give you my opinion of what I would buy. I'd first look at the brands and determine the PAR rating for the bulb using the ballasts you currently have. Different ballasts will output different amounts of PAR using the same bulb. Id want something that outputs a lot of PAR. (10k) Especially since you will be running 175W bulbs over a 190G tank. If you don't like the white look you could add some VHO or T5 actinics to give your tank that bluer look you are wanting and not sacrafice the par output.