130-160€ CPU for R9 290X

You don't list the motherboard. If it's only the CPU you are limited by the motherboard socket (see pcpartpicker).

If you want a CPU that your current motherboard doesn't support it will cost a lot as you'd need:

a) CPU
b) Motherboard
c) possibly DDR4 memory (if you have DDR3 now and get a modern CPU)
d) possibly new Windows copy
e) would also have to REINSTALL Windows and all software
 


 
I was thinking on getting a 70-80€ mobo and 8 GB DDR4 RAM but I got 160 € for it so dont worry. I just wanted to know on that line of price what would be the best cpu for the potencial of an R9 290X. I have like 300€ for mobo+cpu+ram if you want to give me a budget (Price will be diferent because Im from Spain)