Was very happy to find this program as I was considering writing a similar dupe killer program.
Even though your program has some useful features that I hadn't thought of, there are two features that I still wish it had.
Dynamic Range Comparison:
Too many times I have discovered dupes that were remastered/remixed and presumably better than the original. But as many of these have been compressed to sound louder, and therefore have had their dynamic range destroyed as a result.
Signal to Noise Ratio:
This would help to find poorly recorded (from analog) dupes.
Tag vs. Path/Filename
Comparing how much that the Path/Filenames agree with the tags.