DeckLink HD Extreme 3D

Is a DeckLink HD Extreme 3D card, alone, enough to use DaVinci Resolve properly ?
Is it really necessary to use a second card with it ?

First you need a "GUI" display card in your computer. This is what you connect your computer monitor to. You already have this.
Then for more processing power for resolve to play more complex corrections at real time you should add a Cuda capable "gpu" card ( this is another video card and you do not hook up any monitors to it, resolve just uses the processors on it)
Finally to output resolve picture to a calibrated broadcast monitor (like a professional Sony, fsi, etc) you need a black magic card like the decklink you mentioned, but any current black magic card should work. This is so your corrections will look correct in other professional environments. If you are just learning the controls or grading for web you don't absolutely need this
But all this is clearly defined in the configuration guide

Thanks for the answer.
The Decklink HD Extreme 3D is a capture card before all.
For color correction in DaVinci Resolve, I guess an Ivy Bridge HD4000 IGP ( GUI)
and a GeForce GTX 580 ( processing) will do the job.

Well "capture card" is becoming an outdated term as media is provided on tape less and less. So they become more of an output card.
Don't even remember last time I "captured" media...

Use to work time to time for a restoring videos company.
Capturing ( & deinterlacing) and restoring tapes, of weddings, birthdays and even documentaries actually.
DaVinci Revival is a great tool by the way !

http://www.blackmagicdesign.com/products/davincirevival/software/

Do you know anything about the Decklink card running with an AVID Nitris box? Are there any tech issues surrounding running two cards?