Found this great find on Nexus; Texture Optimizer (http://skyrim.nexusmods.com/downloads/file.php?id=12801).
I have a GTX 580 1.5gb but with texture mods I was always hitting the max and so it caused constant stuttering unless I used the Bethesda HD DLC textures. So I tried this optimizer out as the author and the comments from user report 0% image loss but substantial reduction in texture size and thus vram usage.
In case this means little to anybody, each graphics card has so much video memory to store textures so when this is exceeded, as in the cause with high-res texture mods, it causes a lot of stuttering as there is less space than what is coming in and from my understanding the traffic will be continually swapped between the video memory (vram) and the ram on the motherboard. Therefore reducing texture size will reduce stuttering if your close to maxing or maxed your vram.
I used the optimizer and I seen a 12% reduction in textures and it only took 15mins to do. Instruction on how to use it are on the page, however Win 7 64 bit users like myself need to download an extra nvidia tools file and install it but its easy and is also on the nexus page.
My game has never been smoother, its so smooth I can't believe it and I never max my vram usage now even with 3x3 supersampling set in Nvidia Inspector

Hope this helps!
