snd-powermac is not built in for a reason.. snd-aoa is the newer driver and supports the G5's better.snd-aoa and snd-powermac modules conflict and to save from people blacklisting modules, i removed the older snd-powermac from the build config. snd-aoa should work straight away. if it doesn't, check if something has been blacklisted previously.
Regards, Peter