what' your favorite movie to show off your sys. w/

Cliffhanger has an amazing Helicopter scene at the beginning wich will let you know how they reproduce very honest sound, the others mentioned are fantastic also, The League of Extraordinary Gentlemen is great also.

Fifth Element (superbit) and now Sin City

The Matrix, lobby scene and ending with the helicopter crash.

For color balance/saturation: "Black Narcissus" (Criterion version).

For multi-channel sound: "The Last of the Mohicans".

Agree with many above but here's few more:
The Tommy Gun in Road to Perdition is pretty awesome (the music is excellent too).
Band of Brothers, Saving Private Ryan, Black Hawk Down are all sonically outstanding.
Airforce One is pretty cool when the Jet engines roar from the back of your room to the front.
My favorite music video is Stop Making Sense- Talking Heads.
BTW- The new Cream that Theo mentioned sounds like as must buy.