I think you need to read more about where the games get the juice. THIS IS STILL TRUE:

"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. "

There is a deep issue with laptop dual SLI setups. Can be twitchy, hot and if you ever try to load another Windows most folk melt down.

While the 17 and larger screen is nice for a desktop, I find students that buy such and regret it.