Its so hard finding benchmarks similar to your rig to compare. I dont think any of us are really going to be able to convince you to upgrade or not, but you are about 5 generations of Intel CPUs behind and about 2 or 3 AMD generations behind.
Not only would you get a good performance jump in FPS alone, but there are improvements in other areas too.
Motherboard chipsets are better, BIOS (UEFI) . SATA 6 gb/s, DDR3, overall lower power consumption, less heat, completely new CPU architectures, PCIe 3.0 support, etc.
Unless you want to overclock you could do a build with an i5 4430 or 4570, good H87 motherboard, and 8GB of DDR3 memory at 1600mhz or higher which would come out to being just below $400 USD.
Or you could jump over to an AMD FX build with a FX6300/8320/8350 and it would be even cheaper than the Intel Platform.
Honestly you are due for an upgrade regardless IMO. But then again you need to be able to make the judgement yourself.
I am just one of the few that tries to have the best most recent stuff each year even if I dont need it. Im at the point where being behind just a single generation bothers me. Especially on GPUs. I just have a big obsession with hardware is all haha.