RAM-wise, you're fine; minimum is 6GB, recommended is 8GB. As long as your OS is 64-bit Windows (7, 8, etc.), you should be fine there.
Minimum CPU is a Phenom II X4 940, recommended is the FX-8350. The FX-6300 is significantly better than the Phenom chip (http://anandtech.com/bench/product/80?vs=699), but not too far below the 8350 (http://anandtech.com/bench/product/697?vs=699), in performance.
Graphics-wise, they're saying minimum of an HD 7870, recommending at least the R9 290. Your R9 280X significantly outperforms...
RAM-wise, you're fine; minimum is 6GB, recommended is 8GB. As long as your OS is 64-bit Windows (7, 8, etc.), you should be fine there.
Minimum CPU is a Phenom II X4 940, recommended is the FX-8350. The FX-6300 is significantly better than the Phenom chip (http://anandtech.com/bench/product/80?vs=699), but not too far below the 8350 (http://anandtech.com/bench/product/697?vs=699), in performance.
Graphics-wise, they're saying minimum of an HD 7870, recommending at least the R9 290. Your R9 280X significantly outperforms the 7870 (http://anandtech.com/bench/product/1034?vs=1041); it's not quite as good as the 290 (http://anandtech.com/bench/product/1068?vs=1041), but I think it will really come down to the resolution your monitor can get. If you're at 720p or 1080p, you will probably have playable FPS at ultra settings (not the best, mind you, but at least in the 40-50+ playable range). Higher settings might be kind of iffy, but since it's not even released yet it's hard to say.