Ah yes, wish I thought of that. Good suggestion. Only problem is if the PC is off, you'll have to plug the speakers into the Mac.Does your pc have a line in?
Run the output of the Mac into the line in and then have your headset connected to the pc. Should hear sound from both computers.
I used to run my radio into the line in and it worked ok. Just make sure it is not muted, I think by default the Microphone and Line In are muted.
Ah yes, wish I thought of that. Good suggestion. Only problem is if the PC is off, you'll have to plug the speakers into the Mac.