Beck - Soldier Jane from "The Information". This is a superb test of sound stage and detail.
Boards of Canada - Dayvan Cowboy from "The Campfire Headphase". Great test of timbre, instrument separation, and high frequency detail.
The Orb - Abstractions from the Japanese edition of "Bicycles and Tricycles". This track is capable of the most amazing 3D wrap around effect from a stereo source that I've ever heard. On a truly capable system, its mind blowing.
Stereolab - Metronomic Underground, Miss Modular, Three Women, Blips Drips and Strips, Captain Easychord, The Black Arts, Margerine Melodie. If a system sounds great with my Stereolab favorites, it usually sounds great with just about everything.