After bug 323911 I was considering how to go about bug 261841. But there's no better or more flexible way to fine tune sound notifications than the message filter based ToneQuilla. Should be built in. Maybe even enhanced to include customizing popup notifications in the same way.
One small issue, on linux at least, is that not all of the packaged sound files work; applause.wav does not while drumriff.wav does. The .mp3 file opens a default player.