Question Looking to upgrade

[Joet00]

I'm looking to improve my pc a bit and I'm wondering where i should start for a nice boost in my pc's performance.
Windows 10 64 bit
ASUS Z87-A
Intel core i5-4670k cpu @ 3.40ghz
Radeon RX 580
16GB corsair vengeance pro DDR3

 

[CountMike]

I'm looking to improve my pc a bit and I'm wondering where i should start for a nice boost in my pc's performance.
Windows 10 64 bit
ASUS Z87-A
Intel core i5-4670k cpu @ 3.40ghz
Radeon RX 580
16GB corsair vengeance pro DDR3

For keeping MB, i7 4790k, otherwise new system is in order.

 

[julienruc]

What performance are we speaking off here? I'm assuming gaming?

It would help to know the rest of your system's specs as well.