Average differences between a 3570k and a 4690k at same clocks is roughly 5-10%. In game that equates to 0 fps if using a gpu that puts you over 60fps at 1080p on a 60Hz monitor. At worst you are looking at @3-5fps. That's negligible to the point where if you had 2x systems side by side playing the exact same frames at the same time on 2x monitors, you couldn't possibly see the difference.
The only difference you will find between i5 and i7 is on some few games like bf4 multi-player, those will take full advantage of multiple cores, using upto cpu maximum, so a 8 thread cpu is a bonus. Other than that, most games are single thread optimized, and will only use 1-3 cores generally, with any rollover on the 4th.
Having a 3570k isn't gonna hurt at all, and you are in better shape than most running fx Cpus.