bottleneck performance?

[Ooshima]

Bloomfield was quite weak and didn't overclock that well. I'm using a 6 core sandy bridge that I have clock at 4.6Ghz, which was quite a jump from previous generation. Newer generations CPUs only had around 10% increments in performance and didn't overclock any better.

I plan to upgrade to Skylake in the fall.

Skylake doesn't even provide that much difference from 4790K. Unless you are referring to Skylake-E (since you are on Sandy Bridge-E), maybe that's worth it.