I'm a m3tag fan (I contributed on greek translation also).
It looks to me like Winamp doesn't support non-standard (or used-defined) mp3 tags. E.g. SortArtist etc. Also multiple values tags are not supported in Winamp.
Isn't around any winamp plugin or even some other mp3 player that does this.
I am looking for this for loooong time but nothing found so far.
Any thought guys?