I flashed my V6800 DDR Deluxxx. Asus has an excellent utility that runs in Windows (no, not DOS). If you want to use an non-Asus GeForce bios then you'd better go to GeForce FAQ and read up. Personally I wouldn't risk using a generic nVidia bios unless you are VERY comfortable with what you are doing. No offense meant but the fact that you are asking this question suggests that you should stick to the Asus bios.
Oh, just looked at the new and unimproved Asus Taiwan software download centre. What a dog's breakfast. The only V6800 bios shown is for the V6800 Delux and I can't find a note stating whether it is also meant for the V6800 Pure but I would bet that it is.
Try Asus Germany. It's a little better organized. You want
Asus Germany VGA bioswhich I can't access right now. I keep getting Access Denied. They're probably screwed up after having those "l33t hakerZ" attack their site. I can't access the Asus USA site. There is a file in the German ftp directory named a68p04a.exe and an index file.
If I get better access to Asus and find a more definitive location, I'll post again. Good luck.