Sapphire HD 7970 Toxic 6 GB @ techPowerUp
 

Sapphire's HD 7970 Toxic comes with 6 GB GDDR5 memory, a large clock speed increase out of the box, a "Lethal Boost" button to increase performance even further, and a large dual-fan cooler. In our testing this monster delivered the highest single-GPU performance we've ever seen, overclocking worked well, too.

http://www.techpowerup.com/reviews/S...70_Toxic_6_GB/