Allan,
The reason I did the XOvers outside in a separate box was simplicity of installation for me. They were big, some caps were very big, so it was the best way to do things. Not the most elegant. I wasn't worried about "microphonics".
I also just checked in the map Albany! I've been to Sydney, I have family that lives there and further up in Port Stephens, I've also been to Perth, but you are truly in the middle of nowhere! It must be a paradise there! My brother has a kitchen design and building company in Sydeny. They do a lot of fabrication. I wonder if they can help with he speakers or it is not useful. Let me know.