Xeons and Opterons are for the server marked.
Note that; Athlon 64 (socket 940/dual channel/128bit edition) is identical to Opteron 1xx except for the name/label/string id/QA. Athlon 64-940 can run on Opteron 1xx nForce III motherboard (socket 940).
Nvidia’s nForce III(Socket 940, dual channel solution) supersedes nForce II 400 Ultra (Socket A, dual channel solution). K8 (i.e. Athlon 64 754) single channel solution replaces nForce II 400(non-ultra) targeted market.
I don’t recall nForceIII is targeted for the server market (i.e. includes a 8X AGP Pro slot).