The card that compares to the 6800Ultra is the x850XT (non PE) . It ties in 82% of all tests, and wins 10% of the others, and loses the others.
HOWEVER, I would not go with BFG, they are crap. I have gone through NINE (9) BFG GPUs in my lifetime! I have gone through 2 MSI, 1 eVGA, 3 ASUS, 0 Leadtek (just now using them and LOVE them!), 4-5 (can't remember...
) Albatron, 1 Gigabyte, and 2 AOpen. So BFG is by far the worst. I would stick with Gigabyte, ASUS, MSI, eVGA, or especially LEADTEK!!
Here is an eVGA one (PCI Express though, hope that is what you want!) for under 600!!!