No...6800GS is a different core than the other 6800 so there are no hidden pipelines to unlock
Most people here will say the 6800GS because this forum heavily favours nvidia, but it should be noted that the x800GTO is a good choice as many of them have been known to unlock and overclock x850XT PE speeds with a bios flash and a bit of tweaking, which is a huge performance gain for the price you pay for it