The 3d-xl gives you a bunch of different configuration options. There's the dual-projector vs 1 projector thing, but even beyond that there are several options for glasses.
-Easy: just get DLP link. Downside, you have to sync them sometimes when you start.
-little bit tougher: get a VESA compatible emitter and matched glasses (ie, samsung emitter/glasses). Harder and more expensivebecause you have to have the emitter in the setup, but it gets rid of the need to sync
-More advanced: Passive glasses. You'd need to get one of the active polarizers icester sells to mount in front of the lens, the run a sync wire to the vesa port on the 3d-xl. Then you'd need a silver screen. But the upside is you get to use MUCH more affordable (<$10) glasses!