[Build Help] Worth upgrading or get a new system?

Hi there, this is what i currently have:

i5-4590 (3.3GHz)
8gb RAM
NVIDIA GeForce GTX 660
z97 (motherBoard)
1920x1200 Monitor

It can run older games no problem on max (on 1920x1200), but it struggles with newer ones.
I got EVERSPACE, Dreadnaught and Battleborn recently and all of them gotta be tuned to low-mid settings to run @60FPS

I am not really caring for ultra-high settings, but low-mid definitely look like crap :( so i would really like to achieve ~high settings in those games.

• Does it worth of upgrading (performance to $$ ratio) cpu to i7 and gpu to something like GTX960 or would it make sense to just wait it out and build the whole system from scratch all together?
• Would upgrading only cpu or gpu give me enough power boost?
• do i need more RAM :)?

Thank you all.