I currently run a Nvidia GTX 760. I also have a AMD 6 core CPU. Which is more than enough to run stuff that you will want in my opinion. If you're willing to spend money then get the 970, but also keep in mind that if you upgrade to a graphics card that is more than what your PC can handle, then you might have to upgrade other PC parts as well. Mainly just your power supply will probably need to be upgraded.
Tl;dr: Never can go wrong with Nvidia GPU's.