I am planning to buy a GTX 980, however, I do not know whether it will work ok. The i5-3570k seems to work fine with the GTX 980 and since the FX 8320 brings the same performance. I don't think it would bottleneck. Can anyone confirm this for me?
Overclocked an FX 8 core will be within 3-5% of an i5 or i7.
I recommend you check multiple sources, not just one game.
Tom's recent reviews of FarCry4 and Shadow of Mordor are good examples. FarCry was 73-74 FPS vs 78-79 FPS on average. 4-5 FPS...right at 5.5%. Shadow of MorDor was within 1-2 FPS of each other.
It's not a bottleneck at all if you upgrade to Windows 10. I'm seeing 20-30 fps differences in a lot of games I'm playing after the windows 10 upgrade. My minimum frame rates are a lot higher than they were before, which is nice because games play a lot smoother and don't stutter like they did before. I have a fx 8320 paired with a gtx 970.