If someone would prefer the for some reason then they shouldn’t be dissuaded by the GPU used. A single D500 is plenty fast enough for UE4 & they are intended to be so, they aren’t hobbled for games or specifically designed for CAD. The 's cards aren’t related to the earlier Windows FirePro lineup AFAICT - they appear to be derived from & perform like the 7800/7900 series GPUs. For comparison they should be faster than the older Nvidia GTX 775 & 780 Mobility GPUs used in the non-iMacs but are likely slower than the newer AMD GPUs used in the iMac’s.