Cool, thanks for the pics. If you don't have enough room behind the dash, maybe instead of the fiberglass you could use the under seat console floor instead and screew everything in there? You can build wall to mount things sideways too, to save some room. I suppose you can run a lot of those wires under the carpet too, of under/closer to the door seals? It's important to try soon to trouble shoot sound interference and the needed cable lengths too.
Good job with the pictures, makes it easy to visualize everything. Good luck returning the power supply.
PS. Don't forget to warn the service guys about the repositioned OBD plug, that's the first thing they'll look for. Might save some extra time of service if you unplugg everything they're going to use. Just a thought.
Keep us posted, thanks!