Is the GTX 570 worth it?

I am currently running a 2009 Mac Pro with a 5870 GPU. For most basic stuff I do its a fine card, but i am now doing more stuff with camera, depth of field, and 3D inside of AE. I came across the GTX 570 cards from macvidcards on ebay and was wondering if these cards will give me a nice boost when working with stuff in real time in AE. I have an animation that uses Element 3d and when trying to move the camera around it is very slow. Can the GTX 570 help with such things?

Thanks!