Im on the same boat in this one… Tried mp3gain but didnt like it. i got the impression it made songs sound a bit “dull” plus i could still tell the difference in volume between a quiet one and a loud one that got modified. Maybe I should give platinum notes a try.
So far Im using a different solution, a program called breakaway audio enhancer. It basically takes over the sound card you assign it to and normalizes the volume on the fly. It doesnt alter the files. it also has several presets for eq and makes the sound much better. I wish they could do permament changes to the mp3s but they dont. They only trouble is that the gain from the programs and eq mid/treble/bass adjustments will not work effectively but you will never have to worry about volume ever again. They re meant to have a dj version as well that works with popular dj programs. maybe i should check it out.
Funny enough i also use it watching films so i never have to struggle when people are wispering or turn the volume down when the big explosions kick in and my windows start vibrating from the bass lol.