Jay, pace is part of PRaT, Pace, Rythym, Timing. It's of British origin, and places more emphasis on getting the music right rather than "hi-fi" sound effects like soundstage and imaging, which are really studio artifacts and rarely present in live music.
Linn suggests listening for pace by attending to the tune - can you sing along; following individual instruments - can you pick them out? Pace helps deliver the correct emotion with the music.
Maybe the best source for this is an article by Martin Colloms in Stereophile from about 1992. It's available in the Stereophile archives on line.
Also must reading is a two part article in the Jan and Feb 2000 issues of Stereophile by Markus Sauer, "God is in the Nuances."
The European press is full of references to pace.
Rod