Heh, I recently went into detail about how I have my heavily modded Skyrim installation running in a video I made and posted here. I'm using a GTX 760 4GB edition. In interior cells I get 55-60FPS, exterior cells have an average of 35 while less demanding areas get 45 and a few insane areas get only 25.
Yup, this. Whiterun and Riverwood are two places that drop me to 25. But I just can't turn it down, it's so purdy. I'd love a faster GPU so I can have 45+ FPS in those demanding areas buuuut broke college student. I can wait patiently.
I am running a slightly more OC's Nitro R9-380 OC edition @1080 P at last check, I had an ENB and around 45 mods. Have not had any real troubles performance wise. I have had some minor frame drops, but it is not a game breaker at all. I am also running an OCd 8320 and 12 Gb of RAM. which is a medium grade system.