My main reason for buying this cable was because I wanted to use RGB scart for video, but send the audio to my surround amp. Before buying this I was using the official RGB cable (which is simply just a scart cable) and sent the audio from my TV to my amp, which of course suffered degredation.
Audio quality wise this was a big step up. I'm not particularly an audio buff, but I got a Belkin Blue Series 0.9M RCA cable and wired that from the audio out on the base of the scart cable to my amp, and the quality is much improved. You obviously cut out a lot of cable and any processing or degredation from the TV itself (but I think half the battle is having a good RCA cable too).
You will also notice gold plated connectors. The image is as good as, if not better than the official cable. I usually steer clear of third party stuff because sometimes it tends not to be as good, but this is a quality cable.
It also doubles up as a composite + audio cable, but obviously Nintendo supply that with the Wii, though this may be a bit better quality if you are absolutely stuck with composite, however I didn't test that.
I would check this out if you want high quality audio. It's also cheaper than the official cable.