In terms of gaming aspect, I would suggest a newer GPU that runs on a newer architecture. This will help in performance as well as power draw from the system. With the new technologies and innovations that are emerging within the pc component industry, that PSU should last you a while (unless you decide to go SLI) which is loosing support from Game makers so its kinda irrelevant now. Perhaps a GTX 1070. While all these other people are suggesting RAM, unless your Content Creating and video processing, the 8gb of DDR3 should be just fine for gaming. A New GPU will provide your PC with more performance and a lower overall power draw. If your content with the system you have atm, might I suggest a VR headset of some sort. You clearly have the machine to support such a device, and the Oculus Rift with Vr is on sale for $399 including the touch controllers on Amazon. This packages also includes a 100 dollar amazon gift card essentially bringing the price down to 300 bucks.