Hmm... I run an i5 4670k @ 4.2GHz, when looking at the ground in atmosphere I get around 30-40 FPS with the Bluedog Design Bureau Saturn V (50 or so parts), but when I'm in an orbit above 100km (when the ground models don't load and it's just a texture on a ball), I get around 100 FPS. I do run SVE clouds at 8k textures and SVT at 8k terrain textures. If you run 4k textures, I guess maybe 45 FPS on ascent when looking at ground and 90 in orbit or when looking away from the planet for around 50 parts, and halve that for 300 parts I guess. When I get home I'll clock my processor to 3.7GHz and do tests in 8k textures maybe.
@Robotengineer Yes, you would get framerate increases, but wait for AMD's Ryzen processors to come out. They very well may smash Intel's performance for a lower or similar price, they are coming out in Q2 of 2017 I believe for the cheaper ones and Q1 for high end I think, not certain.