MediaMonkey [1] is awesome to find something. It's mainly a music organizer that just happens to be able to play music but it works great even with scattered single mp3 files. Autoplaylists [2], scriptable and extensive search options. Been using it for over 6 years now and never looked back :)
[1] http://www.mediamonkey.com
[2] Autoplaylists are only available for the Gold version.