For gaming, you don't need to upgrade the CPU. In single threaded applications, which include most games, the i5 is outstanding. Overclock it if you haven't already, but that's about it. An i7 is not going going to give you a meaningful difference for the money you'll spend. Use HWMonitor to check your temps and Cinebench or PassMark if you want to check the performance.
https://www.passmark.com/
https://www.youtube.com/watch?v=Kw-qyZB8qtk