Monitor resolution and refresh rate would be good to know, as well as the kind of games you're playing.
Is that a 2 GB or 4 GB GTX 960?
you're better off upgrading the GPU first IMO
GPU, Also consider a 144hz monitor. If you are a fan of FPS it is a must! You will see a huge difference.
which is how much???
@CVLLXM
what's the rest of your computer specs?
mobo, RAM, storage and PSU in particular.
also, how happy are you at DIYing an upgrade?
what does it say on your mainboard tab of cpu-z?
also important to know what PSU you have, as it will affect what graphics card you can upgrade to (more powerful GPUs naturally require more power to run)
that's a bargain basement PSU.
i mean it'll run lower powered graphics cards...but i honestly suggest it'll need upgrading along as well as the GPU.
i wouldn't trust it running a mid range GPU (like a rx580) tbh.
another thing...need to see your case.
care to post a pic?