i dunno about the 6800's mate, as nvidias still got the bring out there 560, 570 and 595 if the latter ever happens
and it will be close with the 6970 and the 580 but considering nvidias still using fermi and its took ati a whole new architecture to compete and this time there late to the game
and the 560 i think will prob be based on the gf104 as its not at its peak its only got 336 cuda but the gf104 can go 384 so an extra 48 should provide quite a boost plus i thnk they will make 1gb and 1280mb cards with 256bit memory, the 570 will prob lack about 40 cuda cores compared to the 580 and maybe run with 1280mb ram with higher end ones being 1.5gb, all in reference flavours obviously