Stereo Tool

I am using Stereo Tool with SAM Broadcaster for my online Stream.
I had used MP3 Gain for a while to normalize all my audio files, but I heard from a few people that it isn't necessary and it makes the files sound worse, especially if I'm running Stereo Tool anyway.
Does anyone know if it in fact makes MP3 files sound worse? And would I gain anything from using it, if I'm running Stereo Tool anyway?
If it can't hurt, I might just use it, even with Stereo Tool, but I don't want to mess up the quality of my files...
Thanks a lot!

It doesn't change the sound of the mp3 at all, just the signal level, which is why it's kinda neat.

But a playback that supports ReplayGain, and R128Gain, is really where it's at. And even with audio processing, it does make a difference because the processing can be relaxed because you know that the input will be within a certain range, and when things get mixed together like two songs or imaging or commercials... nothing will be a lot above or below the levels of the other, so the processing will also sound more stable even when its adjusted to be less aggressive.