if you are doing CAD and only(no gaming), so buy cheapest workstation card - it will act much better than usual gaming card. Reason is(among many others), that autocad uses Open GL, and pro cards have same performance in GL as in D3D(when gaming ones have 1/5). And stability gain by its drivers will impress you, believe me, plus good support from manufacturer, nvidia or amd, and from Autodesk(because with those drivers you should encounter 0 problem such as crashes, and if you got any - they will really support you)