Yes, I know the GTX 750ti is almost double in performance of the 550ti, and from what I've gathered the normal 750 (non ti) is about 5-10 frames per second slower then the 750ti.
I don't know where you are but look around because there are a lot of newer options available for pretty cheap that would be a better option then the 750ti such as the GTX 960 or 970, or in the AMD market a RX470, RX570 etc. You can even find pretty cheap 10 series cards like the GTX 1050ti pretty cheap used.
Just be sure your power supply is adequate for the card you plan on upgrading to.