If you stick with Nvidia, and under 200 EU, then go for GTX 960 2GB. You can try 970 or 1060 but your CPU & RAM may bottleneck them but no one can tell until you start running some games.
Again, the new generation RX 480 is better than the older GTX 960 in everything.
To give you some insights:
I have the i5-4690 + 960 4GB
For R6Siege, I am getting 60-100 FPS at medium/1080p with texture & shadow on high.
For Battlefield 1, I am getting 70-80 FPS at medium default/1080p.
With 750ti and 60 fps you may end up doing Low.