Lighting

I have been having some pretty heated debates with myself, over the wattage of lighting that I would like to use in Lumen Bright Mini Wide pendants. I want to hang my pendants at least 24" above the surface, and maybe even an inch or two higher.

I know this sounds extreme, but my tank will be 36" deep, so the spread will be important. Now, the arguements have been over 250w vs 400w bulbs and ballast. I feel like I will need 400 watters to achieve the results that I have ...