Well, I ordered two 400w 10K Hamilton mogul bulbs. Looking at on-line descriptions:

Hamilton: Crisp Ice White appearance, full spectrum - the combination of different wavelengths produce different colors in the spectrum and appear to the naked eye as crisp ice white light. Significantly brighter than U.S. made 10000K bulbs

XM: The crisp-white color will illuminate your tank nicely. It is very similar to an Ushio10,000K bulb but slightly more yellow

We shall see ...