For anyone looking online, take a look at whiteflash.com. I learned of it on pricescope (the sf of diamonds). They specialized in what some people call super ideal diamonds, which are apparently the top 1% of diamonds (haven't verified that but it's probably not far off).
Good post, and Whiteflash is great. I was very pleased with the whole process there, and the stone is fabulous. They even sourced a designer setting for me with no extra markup.
They used to do discounts if you mentioned Pricescope too.