Hey,
I would imagine the proper way to do it would be to have the jukebox trigger the existing wav on a different audio output.
depending on what soundcard you have, this may be impossible with your current setup.
you can get very cheap usb mic/headphone kits which function as a second output if you decide to mess with the software and go this route.
Another option (again depending on your setup) would be to re-encode the wav files into one of the unused rear channels and just wire that output to a separate amp/pc speaker set.
this is likely the easier option but assumes you have 5.1 or 7.1 audio output built in
or again can get a new soundcard.
either way, you need more separate outputs. hope this helps.