There is no way how you could ever convert xspf to mp3, i.e. convert .xspf playlists to .mp3 audio song. No xspf player of xspf converter will help you because xspf to mp3 conversion is simply impossible.
Playlists are just special text files that contain list of the actual .mp3 (or any other audio) files to be played in a sequence. At best, you can check the .xspf file using a text editor and see where the actual audio files are located, but usually these are located within the same folder.
Updated: March 17, 2017