Well I'm kinda convinced not to purchase a sound card for two reasons - 1. Logitech Z-5500 seems to have good onboard features as pointed out. 2. Lack of availability of consumer sound cards. Now the question is what kind of connector to get? I mean what do I have to tell the shopkeeper? Just TOSLINK? And will it work with iMac? Do both of them (iMac and Mac Pro) have the same audio processors?