Instead of Office Space, try to find a lesser known but funnier office place comedy called Haiku Tunnel. Chances are, your coworkers haven't seen it.
If you want to show off that sound system, try Behind Enemy Lines. Movie itself is decent enough (I'd give it an 7.5 on a scale of 10), but there's a few scenes where a beautiful surround system is a must, where you hear quiet things in the back as the solders come up on him, or the slightest change in the sound of the dirt grinding under his boots as he walks across a mine field, things like that.
Cameron's Aliens is a good one, and if anybody is anxious for next month's AvP movie, double it up with the original Predator.