Chiphell have released some unofficial benchmarks of the AMD Radeon R9 300 series GPU, codenamed 'Captain Jack'. While not many details were found on the site there were 2 benchmark graphs that compared this card against many others.
Not only does the card perform well in terms of average FPS but it also consumes a surprisingly low amount of power compared to other AMD cards. This card, if real, will out perform NVIDIA's current flagship card the GTX 980 with an extra 9 - 10 fps. This could be a real contender in the high end GPU market.
Just keep in mind that this is only speculation at the moment as nothing has been officially announced by AMD as of yet. We'll keep you informed when and if more information arises.