Years ago when I first got a Sonnet G3-400 and ATA-66 PCI card for my 8500 I had those stuttering issues with audio, Sonnet came out with a utility to slow something down on the PCI IDE card so it went away.

I think the designers for the SATA Mac cards were targeting G3/G4 machines which don't have the same issues as the old PCI macs did.