Should I replace my CPU or GPU?

A perennial question.
Here is my canned approach to the question:

Some games are graphics limited like fast action shooters.
Others are cpu core speed limited like strategy, sims, and mmo.
Multiplayer with many participants tend to like many threads.

You need to find out which.
------------------------------------------------------------
To help clarify your CPU/GPU options, run these two tests:

a) Run YOUR games, but lower your resolution and eye candy.
If your FPS increases, it indicates that your cpu is strong enough to drive a better graphics configuration.
If your FPS stays the same, you are likely more cpu limited.

b) Limit your cpu, either by reducing the OC, or, in windows power management, limit the maximum cpu% to something like 70%.
Go to control panel/power options/change plan settings/change advanced power settings/processor power management/maximum processor state/
This will simulate what a lack of cpu power will do.
Conversely what a 30% improvement in core speed might do.

You should also experiment with removing one or more cores. You can do this in the windows msconfig boot advanced options option.
You will need to reboot for the change to take effect. Set the number of processors to less than you have.
This will tell you how sensitive your games are to the benefits of many threads.
If you see little difference, your game does not need all the threads you have.



It is possible that both tests are positive, indicating that you have a well balanced system,
and both cpu and gpu need to be upgraded to get better gaming FPS.
-------------------------------------------------------------

Your pc is relatively well balanced.
If you upgrade graphics, you should probably look more to a GTX1080 or you may not notice the difference.

If you want a cpu upgrade, consider a I7-4790K on your current motherboard.
Your I5-4460 has a passmark rating of 6600 and a single thread rating of 1946.
A I7-4790K, even running at stock gives you 4 more threads and a rating of 11197 and a single thread rating of 2530. Not very different from a I7-7700K.