Insane3D,
time for you to get an important point - a sound engine that connects to its codec through AC97 bus is not necessarily a stupid CPU driven engine. AC97 is a bus standard, not a programming interface definition.
SiS in particular uses quite an intelligent sound engine that puts very little load on the CPU. So does ALi, while VIA's and Intel's chipset integrated sound engines are completely stupid and consume quite a bit of CPU power.
So yz426, if 2-channel stereo is good enough for you, use it. 100 MBit LAN engines must be full duplex capable btw, the standard doesn't allow anything else. In 10-MBit mode, it's autodetecting what the other end is capable of. It's a bus master engine too, connected to a much faster internal bus than a PCI NIC would be. Use it.
regards, Peter