A suggestions... don't scrimp on bits when converting from one lossy compressed format to another. If your original WMA files are at 128K, for example, convert to at least 192K AAC or MP3 -- doing so will cut down on the degradation caused by multiple generations of lossy compression.
Comments
http://www.dekorte.com/software/osx/SoundConverter/
Use wiretrap (freeware). Run it to record the sound when the WMA file is playing
Now you have the AIFF file on hard drive. Convert it to MP3....
This is what I do all the time with those Windows Media and Real Media streaming audios