Well doc i am running the 980ti with 6 gigs of memory , but you should be holding 60 fps with the card you have. question is what fps are you experiencing and under what settings and conditions.
next i would look into what Bizman said. that is a huge processor and with 4.3 ghz and should be able to handle anything this game has to offer.
next i would check out the heat on your video card. i experienced high heat on my video card until i picked up MSI afterburner program for free and had the ability to set the fan speed for different heat ranges .
this is a link to the free program i use to check my heat and fan rpms .
http://openhardwaremonitor.org/ if you could update us with your settings and conditions and what kind of fps you are experiencing this would help . here is an example of what the open hardware program has to show.

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