Well $60USD is a good price for the 750 Ti. Less than half of a new 1050 Ti.
When it comes to money, you are the best judge on how to spend your money. I will say that the 1050 Ti will not be fully utilized in your system, but it would do better than the 750 Ti and would be better to have in the future if you ever upgraded to a new CPU/Mobo/RAM setup.
You asked a good question in which you will get varying answers.