As this processing of your music collection to obtain a pleasing uniform level for you makes your listening experience that much better then thats brilliant yet I would have a few concerns.
The idea of sameness would be one.....I want to listening to music at a level the musician / group performed at when recorded. Mastering can certainly increase overall levels but thats not its main purpose.
The idea of increasing the levels on say Brian Eno's Discrete Music for example goes against the principle that the music was created by.....this is more philosophical then technical.
Ambient music generally is quiet music that often welcomes the environment it is listened in and that includes open backed headphones, obviously not closed headphones. By increase the listening levels of the music one should also turn up the sound of the environment.
Any additional conversion of the audio degrades the quality. Digital audio has no issues being copied but software will change the source material and not necessarily for the better. Analog does have and its best to convert it to digital one time after the recording is finished. Going for analog to digital and back again multiple times deteriorates the signal.
Now much of the above are mute points in the world of iTunes and Mp3 or maybe not.....Mp3 by its very nature truncates the audio file eliminating important data to get it down to a convenient package size for easy distribution. This suggest that even more attention to the recording and its various paths it takes to get to say a cd or even vinyl are paramount if something of its original quality is still available after its Mp3 strangulation....can you tell Im not a fan?
Im really old school when it comes to this and it goes back to my first high end Quad (UK manufacturer) audio system we had when I was kid.... the system was designed to get the most out of the recording as it was recorded. In other words it relied on the fact that the music was recorded and mastered to the highest standard. I still adhere to this philosophy today.