the only suggestion I got relates too power..
you might want to consider, 30 amp on the the power points at 240v, for power amps, blowing something in the AVR sounds bad, might be cheaper to replace it altogether, might want to check for ground loop, might want to consider power backup aswell..
the only suggestion I could make for the pj, os mount it behind the wall..
I also saw a door into that room, I would be modifying that strut to make access possible from either side of the door..
you can't block access to a doorway regardless of how big it is against fire code, I noticed that small door access point, as good as wood is I'd try to avoid it where possible especially if you live in a bush area, knowing picton, pinjarra area fairly well I'd be inclined to build things out of metal and concrete..
you get a bush fire go through there you'll loose everything..