Well, doesn'T apply directly for the brand/manufacturer, more likely because of the 2x8pin, most cards are on 3x8pin.
390W (or the 1KW bios) are the "most unleashed" for the 2x8pin, but sadly the 1kw bios lacks rBAR support and iirc there was a ram clock bug on it too (stuck @ 3d-clocks)