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Evga don't make ati cards, he's looking at the 6990. I have an Asus 6990 handy if you want the voltage controls, although all 6990's have the Ausum switch anyway.
Iirc XFX said they would honour the warranty if you use the bios switch, some won't.
You may want to check it out before committing to any of the various brands.
If your not bothered then just get the cheapest one, they are all the same.