Daddog, I think the 6600 will come into its own with better drivers. Reason why is the 6600 and 6200 (value card) are designed to run natively as PCIe, the 6800 runs natively as AGP and has to translate to PCIe (when bought in that form). Right now the 6800 is faster simply because it is far more complex and powerful in its hardware and architecture than the 6600 is. But they really havent figured out all the quirks of PCIe yet and it will get faster. Fast enough that the rest of the computer will have to catch up.
As for manufacturers, BFG is right on top, and Gigabyte makes good cards too (although they are better known for motherboards). PNY is one of the most popular, although they get mixed reviews. Some people love their stuff and call them value rockets, others hate their cards. I've owned 2 of their cards, they have worked fine. Results may vary though.