Hi and welcome to the forum.
I agree with the others here, is up to you to know if the system is power/responsiveness is enough for your needs.
Since I believe you have 4x 4GB of RAM (16 GB total), you could upgrade your GPU and your CPU.
But before you do that you need to share with us the brand and model of your power supply (PSU).
If your PSU is from a well known maker and have good ratings, then you could try to upgrade to something like a GTX 1060 6GB, Radeon 580/590 8GB, GTX 1660, GTX 1660 Super, or the Radeon 5700.
Thing is, at this point your CPU will start to struggle and will have a hard time to keep it with your new GPU, specially in cpu demanding games, so thats why a new cpu could also bring new life to your system, and a core i7 4770 or similar is one of the best options to consider. You should avoid the K parts since second hand ones use to go for the same price of a new cpu+mobo+ram.
You could also go the Xeon way.
But in short you need a CPU that have 4 cores and HT enable (so it can handle 8 threads).
Heres the list of all supported CPU of your mobo:
https://www.asus.com/Motherboards/H97PRO_GAMER/HelpDesk_CPU/