I have a drill when I download or burn music files. First I run Foobar2000 to add Replay Gain; then Jaikoz to get everything it offers; then MP3Tag to clean things up a bit and add missing artwork; then I move the files to my audio library; then I run MusicIP (yes, I know it’s old, but Spicefly Sugar Cube and Squeezebox use it). Music IP does a first run at duplicate file deletion as well, and because I purchased the product, it will select the “lower fidelity” files to delete. Finally, once a week or so I’ll run EF Duplicate MP3 Finder to remove more duplicate files (missed with MusicIP).
I suppose the easiest add-on for Jaikoz would be Replay Gain information, and that would save me at least one of these steps. As to the rest of these things, perhaps I could do them with Jaikoz - I just haven’t spent the time to learn how.