Depends on what you've done, or intend to do with that cpu. If you are running stock speeds, I'd go with a amd r9 280. If you have gotten a good OC, to @4.5GHz, then you could push a gtx970. Either card would require a good 520-550w psu. If you have a mediocre overclock, like 4.2GHz then a gtx960 or r9 380/r9 280x would be a viable option.