I had the i5 firstname.lastname@example.org and newer games were starting to get bogged down on my GTX 1080. The i5 was the issue. I upgraded my current system specs. I highly recommend if you can upgrade your CPU. That would be your best thing to do. The i5 will bottle neck the hell out of the new RTX 3000 series cards. Something to think about.
The i5 6600K has not aged as well as the i7 6700K. 4 cores, 4 threads is crippling in the newest games. Even the most recent Core i3 and Ryzen 3 CPU's are 4 cores, 8 threads now. You're going to need a CPU upgrade soon.