The base of the cargo organizer:

All the wood cut to size

The outer frame:

Ended up taking off the top, had it so the subs would face back towards the rest of the trunk, but I figured if I turned them to she they were facing up, I'd have more storage room on the shelf in front of the sub box.
And the (ALMOST) finished product:

Still want to add some drawers in the bottom compartments to make everything easier to get to, and add some carpet/wallpaper/design of some sort so it doesn't just look like straight lumber.
All in all, I think it went pretty well, first time doing a big wood project Ike this, I'm really not much of a handyman lol.
The only downside is that with the sub box facing upward, it kind of kills the visibility out of the bottom of the rear window. Maybe towing mirrors are in my future lol.