The ideal music library application

Here is what an application that organizes my music collection should be able to do (and that iTunes currently can't do):

• Import tags from MusicBrainz
• Normalize song volumes using Replay Gain
• Work well together with iTunes:
• Exchange selection and playlist info
• Access the files at their current location, i.e. the iTunes library
• Export low res versions to a folder
• Work on all platforms (or at least on the Mac)

I don't believe that I'll ever get around to implement all this, but who knows, hope springs eternal :-)

PS: For the export task, I have found this script