point is, your current processor is around on par with the best gaming processor around (i5 3570k), and if overclocked it can even be better than it (the 2500k is a very good overclocker, but you seem to have the non-k version).
Anyway I think the main gripe about your stuff is the board. If I'm not mistaken its H77 chipset does not allow you to overclock the CPU. Yes even the non-k can be overclocked to decent levels if the board has some features.
Boards with z77 chipset usually have a feature called "multicore enhancemnt" or "no-k oc" or whatever, that allows you to run all the cores of the processor at its Turbo Boost clock, which is 3.7 Ghz for the 2500. Then again in z77 (and z68 I think) boards you can raise the Turbo Boost max clock by around 4 bins, up to a total clock of 4Ghz or so.
Check your BIOS options anyway.
If you want to upgrade, take a 3570k, and possibly a mobo with chipset z77. Nothing stops you from buying stuff in socket 2011, but atm it's more or less the same.
While it's new and whatnot, PCIe 3.0 is kind of unnecessary for the hardware you can find around atm. I've seen benchmarks of modern cards on 8x and 16x PCIe 3.0 and on 16x PCIe 2.0 and they show little if any difference (PCIe 3.0 is double the bandwith of the 2.0 so a 8x 3.0 slot is equivalent to a 16x 2.0 slot. For one-year old stuff and modern mid-end, the performance hit is still unnoticeable when on a 8x PCIe 2.0 slot.
Btw, who bleep cares of what system requirements lab thinks? If it runs at max it runs at max, there is no way around that.