Mac Pro GPU limits for Video Editors

I'd like to take a vote as to which GPU you think is the best bang per buck for each program:

FCP 7
FCP X
Premiere
After Effects
DaVinci


I'm partial to nVidia GPUs and assume the hierarchy looks like this:

GTX 680 2GB
GTX 680 4GB
GTX 980 4GB
GTX 980 Ti 6GB
Titan X Maxwell 12GB

Thanks for any and all who participate