Which one is the best?

Solution
A 4300 is the same as a 6300 minus 2 cores and its accessible memory. It's not the cores that'll hurt, you've still got a 4 core cpu, it's the lack of memory. With a decent OC, you'll get considerably better performance, which is true of any of the fx. You shouldn't have any gpu issues, if anything you'll suffer some fps loss on cpu heavy games. Try and limit post processing like anti aliasing etc. Also, some settings like viewing distance and shadows are more cpu bound, so limiting them also can improve fps. The 950 is a good match for your cpu.
A 750ti better than a 950? I find that hard to believe. I personally think the better card would be one that fits whatever psu the op has. Many of the 950 series require a 6pin pcie supplementary power connection and a 400w psu. The 750ti is usually a standalone card and can run off a 300w psu.
 


Ok, thank you, but if you look at my specs, do you think the 950 will cause a bottleneck?
 
A 4300 is the same as a 6300 minus 2 cores and its accessible memory. It's not the cores that'll hurt, you've still got a 4 core cpu, it's the lack of memory. With a decent OC, you'll get considerably better performance, which is true of any of the fx. You shouldn't have any gpu issues, if anything you'll suffer some fps loss on cpu heavy games. Try and limit post processing like anti aliasing etc. Also, some settings like viewing distance and shadows are more cpu bound, so limiting them also can improve fps. The 950 is a good match for your cpu.
 
Solution