Lastest evidence points to Wii consoles lacking optical outputs, meaning no 5.1 surround for the console...

According to official documentation recently supplied to development studios, the Wii will lack an optical output, meaning it will be physically unable to output audio in Dolby Digital surround. "Optical digital output is not supported," states the documentation, delivered to studios developing for the upcoming console.

What the Wii does have is a single proprietary audio/video slot, which will support composite, S-video or component audio/video cables. Games running on the Wii at E3 were using Dolby Pro Logic II, which was the audio system used by the Cube and can simulate 5.1 channel sound.

It's worth remembering the Wii hardware still isn't final, though admittedly the sound system is unlikely to be changed before launch.