Cool link. I think those instructions would work on many motherboards as long as the mobo manual gives the pinout.
For the original poster, the SPDIF connector is needed if you need 5.1 surround as a digital link to a receiver, but if you just want to use 5.1 analog multimedia speakers that use three stereo mini plugs, then you don't need to make that adaptor. Just look in the motherboard manual on how to connect the wires. Typically the regular green port (line out) is used for front two channels. The blue port (line in) is used for rear two channels. The red port (mic) is used for center and subwoofer. After connecting them up, need to go into the Nvidia utility to tell it to use 6 channel sound instead of out/in/mic.