Well a an i7 8700k is about $80-120 on Ebay but from what I can see it would only yield a 10-15% in most games at 1080p and less at higher res. That doesn't seem worth the money to me. I would prob save up more to try and get to a 12th Series CPU and Mobo, A 12100 with a B660 would be a much bigger upgrade and give you scope to upgrade to Raptor lake later. it would cost more money but it gives a better platform, more features and a longer lifespan (you could feasibly get several years out of a 12100 and then get a 3 yr old 13600k and keep that for 2 or 3 more).