If you are going with the 5960, I would go with 64GB Ram instead. You will need the fastest RAM you can afford to get a stable 4.0GHz + OC. I would also go with at least a 1000W PSU if not higher…especially since you are wanting to run multiple video cards.
I would go with the two 760 cards over the 760x2. That way you can assign one video card to viewport and another card to GPU rendering…it’s a big help when in the quick tweaking stage. When doing more final renders, then assign both GPUs to the rendering.
That’s my short, short answer. 