ahh, glad to see you've uploaded the code and build instructions. would there be enough power to use a real pc speaker instead of a piezo?
also JOB WELL DONE 
@ freezedream for real authentic sound you should mount it in a metal box
No, I don't think that it would be powerful enough, however, one could very easily add a Darlington transistor setup or a small amp for that purpose.
EPIC!