Upgrade gpu or CPU?

[romerrr]

I have a system with. a gtx 570 and a Pentium g4400 should I upgrade to an i5 7600k (or i7 7700k if I find a good price on the used market ) or a gtx 780ti (or 970)

 

[pete_101]

Really, you need to do both.
If you're into playing modern games, then you'll get the best performance increase from upgrading the CPU first. There is no point in getting a better GPU when you're probably already getting lag and stutter caused by your CPU, this would only get worse with a better GPU.