Well the PC8 thing that I have just bought is simplicity.
As far as I can make out, it plugs straight to the bike, and the battery, no wires get the chop.
You then have 8 outputs available to use, e.g. extra horns, cig lighter socket, compressor, hairdryer, cuddly toy
If it doesn't, it'll be a very expensive desk ornament.
Why can't you just disconnect the horn, and plug the new ones straight on to replace it. Am I that daft that I am missing something?