Eyefinity supports two, I assume Surround does as well. I don't follow Surround so pure guess on my part. I didn't follow your link but it probably does.
I've heard of people playing RTS and RPG games in windowed mode, but not for "enjoyment and to make full use" of their card. (Full use? It's a 750TI which is the lowest card in the current gen. Crank the settings and you'll get full use.) It's usually to pass items to themselves, or farm gold while waiting between runs. I did a search while staying on the first page and this was the most helpful reply/thread I saw.
http://forums.techguy.org/games/970345-can-i-play-2-games.html