I'm sure you've read this passage:
"Our tests demonstrate fairly little difference between a $225 LGA 1155 Core i5-2500K and a $1000 LGA 2011 Core i7-3960X, even when three-way graphics card configurations are involved. It turns out that memory bandwidth and PCIe throughput don't hold back the performance of existing Sandy Bridge-based machines. "

So you have the i7 so why would you think there's something with the CPU and board that would change which of the all too similar video cards would perform?

As to which card, why not find reviews and compare benchmarks?