Help choosing video card for dual 1080p setup

I have two 24" LCD monitors @ 1920x1080 resolution. I am running an i7 build with the ability to go SLI or Crossfire (or whatever). I basically want a video card setup that will allow me to game in 1080p as well as power both monitors in max resolution for movies, video editing, etc. I've searched Google for a few hours looking for a solution, but I can't seem to figure out an answer for my dual display setup.

Basically, I am wondering if one powerful card (eg GTX275/285/4870x2) or two cards (whatever... 260/275/285/4870/4890...) in SLI/Xfire will do the trick for BOTH monitors?

Or should I get two good cards and run them independently (no SLI/Xfire), one for each screen?

Please share your opinions and especially experience -- I am seeking knowledge of these things.