+1You might end up being GPU limited once you get a new CPU though!!
I would say look at getting a Core i5 8400 or a Ryzen 5 1600 and if you don't have a reasonable PSU,a new PSU too.
What PSU and case do you have?? What drives too - do you have an SSD BTW??
Edit!!
The Core i5 8400 seems faster in GTA V but stock is very hard to get and OcUK seem to be selling the CPU at a silly price too.