Well I have a A8N-SLI Premium motherboard and I have successfully installed the Zephyroth 10.5.2 Rev.2 months now and it's perfectly working with all the drivers from the install. No need to touch anything.
I have it updated to 10.5.5 with Zephyroth's Software update.

No my problem is that I have connected my PC with my amplifier with an optical cable which works perfect under Windows Vista. Is there any way to enable it from Leopard?