Well you do have a AMD CPU so i recommend the Radeon 7870
What brand CPU you are using DOES NOT MATTER! Here's a nice chart: http://www.anandtech.com/bench/Product/550?vs=647
They trade blows for different games, so if theres a game you like a lot from that chart, I would go with the one that is better for that. You can't really go wrong with either one.