Which Trans Music Manager equivalents exist for OS X?
I haven't personally tried it, but AudioSlicer may be a good candidate


  AudioSlicer is a Cocoa GUI application
  for Mac OS X that finds all silences
  in an audio file and allows you to
  split it into several smaller audio
  files and to name/tag them properly.


Doesn't seem to do the Gracenote tag fetching, but you could use Jaikoz (tag from MusicBrainz db) or SimpleTagger (tag from Amazon db) for that.