Ok, so assuming a total budget of $500 for both the GPU and CPU, I would recommend an FX-8350 ($200) and an R9 280X ($300).
If you are willing to go up to $600 then you could potentially swap out the R9 280X for an R9 290 ($400). If you want to go this route I really recommend waiting for the release of custom cooling solutions from board partners however, since the reference cooler on the 290 is terrible.
This all assumes that you already have or can get a PSU that can handle these components.