Jim,
I'm running a 2011 MacPro with Lion on it.
I am outputting via BMD Decklink HD Extreme 3D to a Flanders Scientific LM-2461W 10 Bit color grading Monitor.
I am currently running Adobe CS6 FCP and DaVinci and everything works great.
I also have a Quadro 4000 for my GPU for both Adobe and DaVinci.
My thoughts are if you want to use DaVinci, get a Blackmagic card with SDI out. The BMD Cards seem to play well with everything. Look at Flanders or something equivalent for color accurate monitoring. FSI has the best bang for the buck IMO.
Todd Gill
Editor.Colorist
Digital Post Ink
http://www.digitalpostink.com