Fairly simple to do, although I don't know anything about MAC OS. If you do it yourself, you can do it exactly how you want/need it!
Only real problem to consider would be - what IS a duplicate file? Files of a specific piece of music may have been changed by someone and re-loaded onto the web, maybe even you've done the same with your collection. Maybe renamed slightly, maybe significantly. At what point would the changes justify being treated as a new/different file?
Some of the information can be determined by reading through the midi file and spotting certain things, like text for track names, instruments for Prog Changes, size of file, etc.