I've been researching the 6800 GT too. Just started but here are a few vendors I found so far.
BFG, PNY, & eVGA.
The shop where I buy most of my HW recommended the eVGA, but I'm sure they make the largest profit on it too. They seem to move a lot of eVGA product. I never heard of them so I can't speak to their performance or reliability.
http://www.hothardware.com/viewarticle.cfm?articleid=546&cid=2
http://store.jazztechnology.net/evefx6825ddr.html
The eVGA price looks attractive ~$400 US. The 16 pipelines along with the 256 MB 2ns DDR3 should make this card relevant for a long time. Also only uses one slot & power plug.
Personally I have been happy with ATI products my 9800Pro & 9600Pro are excellent cards. If the X800 Pro guaranteed 16 pipelines @ ~$400 I would stick with ATI.
The GT just might get me to switch this time. Anyone else have an opinion on the GT vs X800Pro?
ZZSpaceman