While looking into buying a new graphics card for the editing, live playback and encoding of videos in the new 64bit Premiere Pro CC, I was wondering about:

1) how and when a graphics card's memory is utilised or loaded?
2) when would one benefit from the higher graphics card Memory?
Would I benefit during editing/live playback, or when encoding and exporting a video?

As of summer 2014 the Nvidia GTX 770 seems a sweetspot in terms of price/performance that grasped my attention. This model is abvailable in 2GB and 4GB versions. I will be using some filters and will be using Magic Lantern RAW 1920x840 @ 24 fps footage timeline for short videos of around 4 minutes. Thanks!