Hey, man, so I checked your desktop on Amazon and there's people who said they installed a new graphics card, but apparently you'll need a new power supply as well, 500w should be enough, look for a little quality for the power supply like 80+ Bronze. And the graphics card, well, those games you named aren't too demanding so you can get like a GeForce GTX 750 Ti or 950 so you don't break the bank, depends on your budget really. Take into account the space inside your case. That would be it because your processor is really good and you've 8GB RAM