What I'm saying is it takes a 670 to max out most games with good FPS.
If you turn on 3D, you lose 40-50% of your FPS.
That means it takes 670 SLI to max out most games with good FPS.
Or you have to lower a few settings here and there to play in 3D with good FPS on a single 670.
Don't worry, it's not that huge of a deal, 3D still looks pretty awesome, even with some settings turned down or off. For example, DoF doesn't really help 3D, as it is just trying to create depth, but that is what 3D does, so turn off DoF. AA isn't as needed, as with 2 images being melded together in your mind has an AA effect of its own. Then you'll just go with high instead of very high or ultra on many games.