Hi I have the latest version (even though i bought it in 2010 lol) Mac Pro, 3.33ghz 6core with 4 memory slot body. Initially Ive ordered it with 3.33ghz 6core CPU and ATI 5870 GPU and later upgraded myself with 16GB of RAM. But I feel the lacking of GPU power when I run games for my spare time on newer GPU hungry games (its also for WOW Mist of Pandaria and Diablo 3, and want to run on full highest setting possible) and I would like to purchase an Mini display compatible, and better power than 5870 GPU card. Without any issue, what is the most easiest and powerful GPU upgradable card out there? What I mean is upgrading the GPU without any hassle, almost like just pop out 5870 and pop in new GPU. I would prefer ATI since I personallt dont like Nvidia. Thanks.