3D gaming generally requires you to choose Nvidia 3D Vision or AMD HD3D ahead of time, which will narrow your choices. If you go 3D Vision, you'll be looking at 3D Vision monitors, mostly made by Acer, Asus and BenQ. If you decide to go AMDHD3D, you'll be wanting to look at Samsung monitors.
For the most part, they are not interchangeable. Do you already have a monitor? If so, what monitor is it?