It looks like the GTX series does support it.
(not my video.. just one I saw you YouTube)
As far as I know you don't need SLI to use Nvidia Surround but in this example they are using 2 GTX 480's.
Nvidia's website states...
http://www.nvidia.com/object/3d-vision-surround.htmlalso enjoy BEST-IN-CLASS 2D SURROUND GAMING.
Game across three non-3D displays with resolutions up to 2560x1600.
Enjoy support for both landscape and portrait mode for ultimate display flexibility.
Might be able to get the best of both worlds using one card.