Original post by: Geoff Wacker ,
Hey Adrian, I found the thread on MacRumors that you pulled those pictures from. GMacUser was able to upgrade to a 680m, and it seems to have worked pretty well for him. However, a 680m MXM is $500-600 online, and a 780m MXM is even more. Additionally, it looks like the 780m that you want to upgrade to is going to take a lot more work to get up and running correctly. The 680m also has a higher TDP (thermal design power), which means more heat inside your iMac. In my opinion, this really isn't a cost-effective upgrade because the performance increase you'll get won't really justify the time and money spent on it.