Best spot to buy the WH7 That I have found online is ReefGeek, that is where I got mine from, more then likely locally you can find a bulb cheaper if you only need one because most places if they ship them charge the same shipping for one bulb or six.
Personally for veiwing astetics I'd go with 10,000k, and Super Actinic03. But I'm partial to having a blueish tinge to my tank. Either combo shoulkd be just as good as each other for inver photosynthisis.