The aging Athlon II X4 640 still has some life left in it for casual gaming. The GTX 950 would be a good choice. My Athlon II X4 645 is able to handle my Evga GTX 960 FTW in most games, but bottleneck is present. But high-end games on a busy server can be a bit much for my Athlon II. (Single player is mostly good). Go with the GTX 950.