The big unanswered question is: what's your power supply make & model?
The advantage of the 750ti is that it's such a low-power card that it will run in almost any machine. With the rest of your specs you could definitely run a 770, 7950 (or R9 280) without have major bottlenecking issues in most games, BUT, those three cards are all pretty power hungry and you'll need a power supply that's up to the job.
Post the details back here and we'll let you know.