What he could do is connect the CD Audio header to the A4000 motherboard header, since the Paula Audio connects to the Prisma header anyway.
True, but the A4000's motherboard header has a weird, non-standard pin layout. I did make up a special cable to fit it a few years ago, but it was very unbalanced, CD audio was very quiet and Paula output really loud. Will be much nicer when the Prisma does it, I imagine.