Of the monitors mentioned, I'd highly recommend the BenQ XL2420T over the others. I see nothing but good reviews on it for both 120hz and 3D gaming, which I personally love.
If you've never used 3D Vision or stereoscopic 3D using HD3D for gaming, you don't know if you like it or not. It is nothing like 3D movies. It's far better. There are a lot of games that support it. Close to half of my games do. If not more than half.
You'll also want to be able to reach 80+ FPS for a noticeable improvement over 60hz TN monitors. The biggest thing I notice is that games are more responsive with less latency. This results in lowering/removing motion sickness issues for me, on top of the fluidity bonus.