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?
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?