Have you thought about AMD at all or are you set on Nvidia. With AMD you get stronger performance with Skyrim in general and that's outside the ram. You also get really good multi monitor support with Eyefinity. For heavy skyrim playing I'd get two 7970's pair them up and enjoy! That and the free games that come with it.
Actually, Skyrim favors Nvidia. Crossfire is known to inject stuttering issues for it as well as not scaling as well. Look at the last chart here, which is the most relevent chart for the comparison here:http://uk.hardware.info/reviews/2725/16/nvidia-geforce-gtx-670-review-plus-sli-and-3-way-sli-the-elder-scrolls-v-skyrim
Note: the latest beta drivers may have fixed some of the issues, but for the past year, it has favored Nvidia.