So I am running an original, somewhat upgraded mac pro from 2007. Waited for years for the new mac pro, then it ended up being more then I really need as I don't do video, just photography. I am planning on buying a 27" imac, and am contemplating whether I should do the 775 or 780 video card. I plan on trying to run my current 27" cinema display on the other side of a thunderbolt G RAID, which sounds like it works from what I've read around the net. My question is, thats alot of screen space to power and should I upgrade to the 780M?