680 vs 7970 GHz Edition and PhysX Help?

[i2iDGE]

So i am making a new build (specs found here) and i was wondering if i was better off getting a 680 or 7970 Ghz. I will be doing a lot of video editing and CAD (AutoCAD), as well as gaming. I am planning to get 2 cards but would lke them to end up being cheaper than $1000, but am willing to spend slightly more if necessary. The 7970s are looking slightly better but can someone briefly tell me what PhysX is cuz im worried about that aspect of the cards, and im also not sure if it is only to do with gaming. The cards im looking at are the Sapphre Vapor-x and the MSI lightnng/Gigabyte Cards. Any help or suggestions would be greatly appreciated!

 

[bystander]

It would seem that Nvidia has a clear advantage over AMD with AutoCAD, though I found other CAD software that preferred AMD:
http://www.pugetsystems.com/labs/articles/AutoDesk-AutoCAD-2013-GPU-Acceleration-164/

PhysX is a physics engine that is used in a number of games and both AMD and Nvidia cards do not play a role in the majority of these titles. GPU accelerated PhysX is something only supported Nvidia graphics cards and Agea PPU's (discontinued). There are only a little more than 20 titles that support GPU accelerated PhysX. For the most part, to get the most out of those 20+ games requires an Nvidia card. Unless you have one of those games, I wouldn't worry about it.