Yes, I agree the AHI and soundcard area can be a bit confusing at first :-)
But the only thing you need is a twin RCA cable to stereo phono plug that you connect to the Amiga white and red RCA connector. Then you need an adapter for the phono plug of the cable to the bigger stereo phono connector (whats its name again?) that the Toccata uses for the input and output connectors.