I got a new PC recently for the same reason and went for a GTX1070 graphics card with 32GB RAM; I was getting fed up with overnight renders (with GTX850). The render times are way down; a single complex figure with HDRI ackground often renders in 2-3 minutes and complex scenes (multiple characters and a complex set) can render with around 2-3000 iterations in less than 2 hours. The upshot is that I can now use more complex sets rather than relying on HDRIs for quick renders so get far more from the hobby. My PC is the ASUS G752VS with Intel i7 processor. I'd say get the best graphics card and as much RAM you can afford!