Request: what should I do to upgrade my PC?

This is my current PC's hardware I'd like to know what I can do to upgrade (dual graphics card or more ram etc, I'm not a pro at computers so I thought this would be the best place to ask): AND fx-8320 3.5ghz 8 core processor ASUS M5A99X EVO R2.0 ATX AM3+ motherboard G. Skill ripjaws x series 16gb ram ddr3-1866 memory 750gb SSD (not exactly sure what it is it was given to me) 1tb hard drive seagate 7200rpm 1x Nvidea gigabyte gtx 960 4gb

I run two monitors (27" 2560x1440 and 30" 2560x1600)

Thanks to anyone's advice

(BTW this only cost my £650 2 years ago as I built it myself for a cheaper build)