There is tons of movies to show off your system. For obvious surround I like to show: Heat (the shooting scene and the airport scene), Star Wars the phantom menace (pod race), The Matrix (from the lobby scene to the explosion of the helicopter), The Matrix Reloaded (car chase), The Matrix Revolution (fight against the machines), and so many more...
For ambiance surround, LOTR trilogy, King Kong, Avatar and one of my favorites is Seven (the New Line Entertainment master), the surrounds are active throughout the whole movie filling the room with ambiance.
