What GPU is the best suited for AMD Athlon X4 860K?
Nvidia is fine and prefered.
GTX 960.
Go with 4GB of VRAM because game devs don't care about optimization anymore (or if you like high res textures. Whatever, it's future proofing), and if you have a mobo with SLI support you can get a second copy or the GPU, though I guess that CPU would bottleneck the performance.