I have actual experience in this matter. Using a GTX 680 2gb SLI setup with the highest quality Ambient occlusion ENB, 2k SRO texture pack, Static Mesh improvement mod, enhanced distant detail terrain, Skyrim Full distant lod mod, HD Trees 4k, and various other 2k+ texture mods and over 100+ gameplay mods: Walking in a straight line gives a constant 60 fps, but loading new scenery while turning in a 360 degree circle causes some stuttering in an object-heavy outdoor location such as right out side windhelm or whiterun. Using a GTX 670 4gb sli setup with the same mods, I get absolutely no stuttering at all. Why? Because my max VRAM usage peaked above 3,262 GB. That means 1.2GB of framebuffer was cached in regular system ram, which is slower than VRAM. I noticed my system ram usage would peak to 6gb. While using the 4gb cards, my system ram did not go higher than 4gb, and as a result, had no stuttering while new scenery was popping in while turning in a 360 degree circle. I am obssessive with skyrim having the highest quality textures and mods, but if you are not as obssessive as i am, just reduce the size of the textures using an optimizer tool. Overclocking the GPU clock speed does not have a very noticeable effect on skyrim since skyrim is more of CPU and memory hog. I wouldnt bother with the 'FTW' or pre-overclocked cards since the cards are easily overclockable on their own. It is up to you wether you can live with a little stuttering in specific situations with the highest quality textures. I can't.... since I'm a little crazy.
