I still don't understand why it would be pointless to buy another 770, unless the difference vast.
Thus I'd appreciate if any empirical results could be shown.
That's complicated, because it really depends on the game and your settings.
For example, I did some tests once myself with BF4 at 1080p ultra settings as a comparison to AMD's Mantle test. My CPU is typically overclocked to 4.5ghz, with stock clock at 3.2ghz and max turbo at 3.8ghz; but only on two cores. Anyway, I benchmarked the most CPU heavy area of the SP campaign (the part when they're on the sinking ship) with my CPU at 4.5ghz and at stock clocks.
With the overclock, I was about 10 FPS higher on average than I was with stock clock, and I never dipped below 100 FPS, whereas with stock clock, I dipped below a 100 a few times.
I was surprised because I thought there would be more of a difference. But when I thought about it, BF4 does use multithreaded rendering so frequency would be less important than actual number of cores.
But if I had tested a game like Arma 3 which uses a single thread only for rendering, the difference would likely have been much more than 10 FPS as core frequency would be much more important.
Anyway, this is a forum for PC hardware enthusiasts, and knowing enthusiasts, they typically want to tweak their rigs to the max to get the most performance out of them..
So when you ask us for advice, you're probably going to be told that yeah, your CPU is limiting your performance. But does that mean that you're going to have crappy frame rates due to your CPU?
No it doesn't.. Your frame rates should still be very playable. It just won't be as high and steady as if your CPU was overclocked..