hm... as i remember from my musicmatch days they had very good library features (though the shit would crash often etc on win98)
what i didn't like about itunes when i tried it was that it wasn't a very flexible program, in general.
nowadays i no longer use libraries-- i put everytihng on a big hard drive alphabetically organized and open the folder straight with winamp.
so what i'd do in your case maybe is search for an itunes plugin of some kind that would add the flexiblity you need.
if you don't know where to start maybe ask the geeks in one of the boards here:
arstechnica AV forum
arstechnica Mac forum
i'd try #1 first...