http://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_670_SLI/
NVIDIA GeForce GTX 670 SLI is an amazing pixel-crunching solution. Priced at around $800, or 20% cheaper than NVIDIA's Kepler flagship GeForce GTX 690, the solution is found to be just 2% slower. Since the GTX 690 performs near-identical to GTX 680 SLI, the inference carries on: it's just 2% slower while being 20% cheaper. As a result, the two other costlier solutions are smoked in the price/performance equation.