Life without optical input I'm upgrading from a Mac Mini to an iMac and am quite surprised to learn that I'm losing some connectivity options. Firewire I can live without, but I quite needed the optical input on my Mac Mini.

I have a PC and a Mac, and one set of speakers. So I used the optical output from my PC to the optical input on my Mac Mini and was quite happy with that arrangement. But it seems the iMac lacks optical input. What options are open to me? I can find professional solutions from M-Audio that would work, but I'd rather not have to pour hundreds of dollars into making up for a missing port.
You can connect the optical outputs of your two computers to an optical switch, then connect the switch to your speakers.

Since most switches have TOSLINK inputs you might need 3.5mm optical -> TOSLINK cables to connect your computers to the switch.

All of these parts are common and relatively cheap.