I really looking to buy one of those new iMac's. At the moment I am using my MBA for serious work and I have a PC under my desk that I really only start up for playing games. I dont like the Windows PC sitting there unused except from gaming and I want to replace it with a gaming capable iMac. Now with the new iMac I am looking to buy either the 21,5" with GF GT 650M or the 27" version with the GTX 660M. The only thing that matters for me really is if the iMac GPUs will be capable of running my games in high detail. That is BF 3, Source games like Portal 2 and TF 2, Diablo 3 and StarCraft 2. I know its not fair to compare those mobile GPUs vs the Desktop (my PC has a Radeon HD 6870). I just wanted to know how much of a performance drop it will be compared to the Desktop and how do the GT 650M and GTX 660M compare?