Dell Precision advice?

I am spec’ing lab computers for an architecture school. I’m looking at these Dell Precisions:
Can anyone advise me on the graphics card sweet spot? I was thinking of the NVIDIA® Quadro® P1000, 4GB, but I’m wondering if it would be worthwhile spending more for the P2000 or for dual P1000 cards.
In addition to Rhino/Grasshopper/VRay, they will be used for various Autodesk products, including Revit, Vectorworks, Lumion, and Adobe Suite. And other CAD/graphics apps.

In our shop, Lumion was the “pushing” factor for us. We were using the M4000’s, but they weren’t performing good enough for us. We ended up specing P4000.