MATBIC  This is not the one for you if you have a lot of duplicates. It will only process about 2000 files at one time. So you have to select them in batches to process them in iDupe. This makes it a very "hands on" affair to de-dupe a lot of files so you have to keep watching it and selecting the next batch of files. It has great functionality when dealing with up to 2000 files at a time. Look at Dupin it handles lots of files in one go, you just point it at your Music folder and leave it to it.

Great software except for this one point.   
(Version 2.5.2)