I have a rig almost identical to yours. I even own an R9 270x. And in terms of raw power, it is far better than the 750 Ti. But I will advise you to save up and purchase an NVIDIA product like the GTX960 because they're dominating PC game development right now. Their GameWorks library is being used in many AAA titles and AMD cards run those titles like shit, simply 'cos NVIDIA has designed the library in a way to cripple performance on AMD hardware.