The terms of "smooth" i think is very different for everyone. FPS around 30+- might look smooth for awhile, but for me, i still will lower the setting to get higher fps.

I agree that fps above 40 is better for game play. At least you can felt that your pc not that tough to handle your game.

Even with a single 5870, everything max out, i still found that a slightly lag while running or in the middle of war. I only able to get 30+- for max out setting crysis/ crysis warhead. This game is graphic hunger.