I've not used the Quadro 600 or 2000 cards, so I really can't give you a comparison, but I will say I've been happy with the FirePro V4900 for (mostly 2D) use with AutoCAD 2012. We don't have Revit, so I can't help you out there either. Maybe someone else can chime in that can better answer your question.
ATI's will give you more bang for the $$$
But I'd buy the nearest Nvidia at twice the price.
I've had nothing but problems with ATI cards/drivers in WORKSTATIONS in the past. Ive tried 3 or 4 times and always end up replacing them. I do buy them for my kids gaming boxes.
But that's just my opinion, I could be wrong.
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