Hindsight is a wonderful thing, but starting with the simplest working system, then adding complexity as testing progresses is often best. With CFX-II removed, starting with the basic sound problem would likely have revealed the fault much earlier and without the expense of the new Propeller and EPROM as well as the VGA cable.
Still, I’m sure that input was great fun and you will have learned a lot!
Happy MTX/CFX-II ing - again

Regards
Dave