gtx 780ti worth the money over gtx 750ti?

Solution
Well. The 750Ti is an entry level, low power card. Hardly considered gaming.
The 780Ti is an extremely high end gaming card, was fastest single GPU out there for a while.
You can see here:http://tpucdn.com/reviews/NVIDIA/GeForce_GTX_980/images/perfrel_1920.gif A comparison of all of them.
The 780Ti pulls a massive performance edge, and the 980 edges out the 780Ti.
Well. The 750Ti is an entry level, low power card. Hardly considered gaming.
The 780Ti is an extremely high end gaming card, was fastest single GPU out there for a while.
You can see here:http://tpucdn.com/reviews/NVIDIA/GeForce_GTX_980/images/perfrel_1920.gif A comparison of all of them.
The 780Ti pulls a massive performance edge, and the 980 edges out the 780Ti.
 
Solution
As said, you need a system to match such as a good Intel i5 CPU (i5-3570 or better preferably).

A GTX780Ti makes no sense any more as a $340 GTX970 can almost match its performance.
http://www.techpowerup.com/reviews/ASUS/GTX_970_STRIX_OC/25.html

Not only that, the new cards run quieter, use less heat, and have several NEW FEATURES.

*Actually if you use the new MFAA mode which isn't as demanding the GTX970 can pull ahead of a GTX780Ti easily. We're still waiting for the NVidia to finish optimizing the code for that but they've said 4xAA performance at what 2xAA would normally cost or possibly less.

That might gain you 10% higher frame rates.