From my personal experience i've found "CAD / Graphic professional GPU's" (ie Quadro, Fire, etc) to be a complete waste of money. These GPU's are marketed as a necessity for architectural workstations from Dell and other manufacturers. Sales people are always quick to point out the the Quadro or Fire gpu's are "certified by Autodesk"..... i don't get it. My experience leads me to believe this is all a marketing scam to get you to buy high priced hardware. If someone can explain to me the difference between a CAD specific GPU vs a gaming GPU i would be very appreciative.
My home computer which i built last year has Radeon 6950's (crossfire is not enabled in Cad or Revit or Photoshop, so lets consider my two cards as simply one) and it performs several orders of mangantude better than my office workstation (Dell) which cost $3,200 and has a quadro GPU (which cost $1500). My home build was sub $2000...
My 2 Cent's... buy a gaming GPU which will cost you significantly less money and perform better in CAD & Revit. This
Geforce 570 fits in your budget and i believe will provide excellent performance/value