You can't play the .msv file on your Mac, correct? You can only hear it played back on the Sony device, correct?
Use the Sony software to convert to .wav file.
Drag the .wav file to an iTunes playlist, highlight it and use the Advanced menu to convert it to .mp3 format.
Delete the .wav in iTunes and delete the original that Sony made to free up space.
WireTap can only record what can play through your machine. The free version default save is .aiff format and these can also be converted using iTunes.