The stuttering and low FPS are caused by VRAM having to swap out texture data back to the hard drive because there isn't enough to room to store all the high resolution textures plus the other VRAM requirements such as Anti-Aliasing.
The bottleneck with moving data in and out of VRAM is the hard drive, it's much slower than the VRAM, so increase in memory clock speeds won't help here.
Your only options are:
1) Decrease VRAM usage, typical culprits here are custom texture packs using a large amount of space, and Anti-Aliasing VRAM usage can be quite high when used on large screen resolutions and with lots of samples.
2) Increase VRAM amount, basically buy a better video card with more VRAM
3) Decrease the time to swap game assets between the drive and the VRAM, that means a faster drive, you already have a SSD so no real improvement to be had here.
If I were you I'd just lower the Anti-Aliasing that will dramatically lower VRAM usage at resolutions like 2560x1440.
Just out of interest i've been trying to find good uses for RAMDisks recently, the Skyrim install would entirely fit into a RAMdisk since you have 16Gb total. I'd be interested to see what sort of performance you get during VRAM/RAM data swap, I'm betting it's way better than using a SSD.
ImDisk is free and easy to use, try installing that, create a 10-12Gb RAMdisk, make a copy of your Skyrim install there and run it from the RAMDisk, report back