G0ll0 :
$130 -$140 .. but it is a 4 core cpu 3.2GHz how can a bottleneck occur?
If OP has a Phenom 2 X4 955, then no he won't see much bottlenecking with a 750ti. It's still a decent CPU for it's age contrary to what you say, and should pair nicely with a 750 ti. You might have a bit of a bottleneck in CPU intensive games, but nothing to serious, especially if you can overclock your CPU.
Don't get the 7790, go for the 750 ti since it's stronger than the 7790 while consuming less power at the same time.