I have a Logitech 5.1 surround sound system that I used on my PC. It's nothing special, under 100 bucks. I was wondering if there is any way I can hook them up to my Intel iMac. The speakers have the standard 3 plugs that plug into a PC's 5.1 surround sound card, but there is only one output on the iMac...Am I missing something? I searched and found nothing, thank you.