I have really grandpa PC setup. My friend now offered me GTX 960 4GB for really nice price. By statistics it should be 250% more powerful, but with my futuristic processor, will that even make a significant change?
I didn't find the right solution from the internet.
To find what bottlenecks your PC thebottlenecker.com/ is good place to start. In most games GPU is more important than any other part of your PC. I recently changed my old GPU (GTX 580 to GTX 1060) and now I can play any game on 60 FPS or more (last game I played is Doom 2016 on highest settings).
Rest of my PC setup is quite old and you can buy parts cheap: i7 3770K cpu 4x4GB DDR3 1333 mhz RAM and old SSD OCZ Agility 2