Natural sunlight is around 6700 Kelvin. The water in the ocean filters out reds, oranges and yellows that are more visible at the lower color temperatures. To more accurately recreate reef lighting you want a more blue color. The lower kelvin 6700-10000 would be more accurately resemble shallow depths. Higher 14000-20000 is better for recreating deeper reefs.
If you are looking for cheaper halide bulbs, check these guys out.
Aquarium Lights - InsideSun
They have 10k, 14k and 20k bulbs for much cheaper than anywhere else I've found. I don't know if their 14K's are listed on the website but you can ask for them if its not. I use their 10K and also their entire metal halide retro-fit which I am pretty pleased with for the price. (I think I paid about 85$ INCLUDING THE BULB!)
Best of luck!