Yes, once converted to iff audio, it sounded better than being played directely as MP3 which sounds more like the tone of a bell. I use a converter program called mp3 to iff from aminet.
This conversion alone can not make it sound "better" ... due to stereo -> mono it can sound DIFFERENT as the soundfield has changed, but no way it can sound better at least when it comes to soundquality. Granted, it can sound better in yours ears depending on audio source (mods have 2+2 channels for example, mixing them as mono might sound more pleasing to ear)
If I paint my car from black to white, it doesn't make it better.. yes, more pleasing to an eye, but not better ;-)