I've just finished my subwoofer install so figured i'd share the process encase one of you guys want to do that same.
This is the boot/trunk compartment that I used. The plastic isn't great as an enclosure for anything too powerful and you can only realy fit an 8" sub but it turned out great for my needs. It's not too deep because of the wheel arch but it's fairly long so gives it a pretty good sound.
This is the sub I used. It's an 800watt 8" jbl. Pretty good for the cost of it. And it will be hooked up to a 1600 watt amp.
I made a template using the old storage tray from the compartment and cut out a wooden plank which the sub will sit in and be attached to the side compartment.
The wiring was a nigthmare and was too frustrated to take a photo. Basically i had to take a feed from the rear right speaker and a feed from the rear left speaker and link them to an RCA cable which was then run to the amp.
The amp needed it's own direct power from the battery so i ran a large red cable form the battery terminal, underneath the chassis and into the cabin through a rubber drain plug underneath the drivers side carpet. From there it was run along the inside of the plastic covers to the amp.
It's pretty messy looking but cant be seen when seat are down and gives me an easy way to add another underseat sub.
I covered the wood in a black cloth which i'm not too happy about because it looks cheap but will do for now. I'll eventually change it for a carpet that covers the screw heads. It's best to but a layer of sticky foam between the wood and the plastic to stop any rattling.
I also had to put a layer of foam between the plastic compartment where the sub is mounted and the glass because of rattling. Aside from this it didn't rattle at all and gives a pretty good sound for an 8" sub.
I think it's good because you can make more use of a useless compartment. The bass isn't the usual thump you get from a normal sub box but it makes a pretty good bang and you dont loose any space.
enjoy