What should I upgrade next?

[MetriMake]

What should I upgrade next?
I can play games like bf4 high graphics 30-40fps, DayZ Standalone 40fps, in cities 20fps (but of course its early alpha so its not stable)
And I want to play games in future in high graphics.

Setup:
Intel Core 2 Quad Q8200 overclocked @ 3.19 GHz
4GB RAM
NVIDIA GeForce GTX 750 Ti 2GB (just bought, old one died)
Windows 7
Asus P5Q SE2 Motherboard

 

[rgd1101]

budget?

 

[MetriMake]

uhm.. maybe something between 100-300$, but if cheaper always better for me