What is your problem?
Is your performance not good?
A game will always be limited by either the cpu or the gpu.
Your test of lowering the settings and getting presumably the same fps, suggest to me that your cpu is what is limiting those particular games.
Be careful how you interpret task manager cpu utilizations.
Windows will spread the activity of a single thread over all available threads.
So, if you had a game that was single threaded and cpu bound, it would show up on a quad core processor as 25% utilization across all 4 threads.
leading you to think your bottleneck was elsewhere.
It turns our that few games can USEFULLY use more than 4-6 threads.
How can you tell how well threaded your games or apps are?
One way is to disable a couple of threads and see how you do.
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, it tells you that you will not benefit from more cores.
Likely, a better clock rate will be more important.