@ Sarah & George:
MBP’s with the GT650M, come in two variants:
1.) 15-inch 2.3GHz NVIDIA GeForce GT 650M with 512MB of GDDR5 memory
2.) 15-inch 2.6GHz NVIDIA GeForce GT 650M with 1GB of GDDR5 memory and automatic graphics switching
Though the number of CUDA cores in the GT650M is way above the minimum of 96-cores, Mercury Playback Engine will only work properly if your VRAM is at least 896MB. Having the MacBook Pro as configured in #2, I’m sure you wouldn’t have a problem running MPE!
Hope this helps…