What do you do with this pc?
If you run multithreaded apps such as rendering then a I7 might be appropriate.
But, I suspect your usage is gaming.
Then, the most effective upgrade may be cpu or gpu or both.
If your games are strategy, mmo, or sims, then you are most likely limited by your cpu single thread performance.
Your i5-4460@3.2 has a passmark rating of 6614 and a single thread rating of 1948.
For those types of games, a I3-6320@3.9 would likely be the most effective cpu change. Passmark is 6073/2245.
If you can afford a Z170 motherboard, a I5-6600K with an overclock would be considerably better.
OTOH, if your games are first person shooters or fast action games, then a graphics card upgrade would be appropriate.
You would want a significant graphics card upgrade. That would be perhaps to a GTX970 class card such as GTX1060
How to tell??
Here is my stock approach:
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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 core. 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 cores.
If your FPS drops significantly, it is an indicator that your cpu is the limiting factor, and a cpu upgrade is in order.
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.
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