I have two Nvidia GeForce GTX 680's in SLI and was considering saving up some money to buy two GTX 980's and put them in SLI. How much more performance should I expect to see? Based on what I've read, the 980 is more than twice as fast as the Kepler. And would an Intel Core i7 3770K (Ivy Bridge) @4.0 GHz with 16GB of RAM bottleneck those two GPU's? Do I really need to upgrade my CPU and motherboard to the latest iteration of the Core i7 processor to handle the massive throughput of these monster GPU's? Is it absolutely imperative to have PCIe 4.0 x16 to properly run these cards?