I've been having inconsistent sound levels with the Apple Pro speakers on my 867 Quicksilver, especially at lower volumes. For example, the alert beep will "fade in," and sometimes quiet music (like classical) will fade out completely. This only happens in OS 9.2 (and now still in OS 9.2.1). However, the speakers perform great in OS X.
I just spent a half hour with Apple's Tech Support, and they had me check the jack connection and zap the pram, with no avail. Anyone else have this oddity? I would think that if it was a problem with the speakers, it would have the same quirk in OS X.