I currently have an upgraded Eight Core Mac Pro 2,1 Dual 3.0ghz X5365 with 8gb Ram and a genuine Apple Radeon HD 5870 graphics card. I originally had the 512mb 1900xt which I upgraded to an Apple Radeon HD 5770 and then last summer upgraded again to the 5870. In all cases, I saw a noticeable increase in performance. Mainly, in terms of graphics useage, I've been playing GTA V and a few other games on Windows 7 Ultimate 64 bit in Boot Camp. It runs very well considering the age of my Mac Pro, hitting a very playable 30fps 85-90% of the time, and only dropping to about 22-25fps in very demanding locations at 1680x1050 resolution. I've always been tempted to upgrade to a flashed 7950, especially for the 3gb VRAM since GTA V easily maxes out the 5870's 1gb. I've done a lot of research but I can't really find any definitive answers: Would I see an improvement in terms of being able to, at the very least, keep my current FPS performance yet being able to load higher quality textures and such due to the increased VRAM if I were to upgrade at some point or have I reached my limit? I figure that I've got to be CPU bottlenecked at some point, but I rarely see that thought up. And, from what info and comparisons I can find, there seem to be conflicting reports regarding if the PCIe 1.0 of my Mac Pro truly causes a bottleneck in these cases as many still see some improvements (at least in benchmarks) when using newer cards, but there isn't much real world useage info that I can find. Anyway, sorry for such a long post. Any insights would be most appreciated!