Buz2b, SB!Audigy also uses AC97 codecs. So? AC97 is just a digital interconnect bus between sound engine and digital/analog converter (aka codec). Everyone uses that standardized bus, that says nothing about how good the components on either side are.
K7S5A uses the "SiS 7012" chipset integrated sound engine, an AC97 interconnect to either a Realtek ALC100 stereo or a C-Media 9738 4-channel codec, and has pretty good analog circuitry behind the codec.
Analog output quality is good, good enough for flawless wave replay and CD listening on a quality HiFi rack. The sound engine itself is a bit sensitive to other PCI cards that block the CPU for too long. Disturbances have been seen with old&slow PCI graphics cards (and stayed that way with a PCI sound card btw).
regards, Peter