How can I get the most out of my Sub and amp? looking at aperiodic enclosure!

[jellymonster]

Hi,

The sub and amp that I have are:
Kenwood Electronics Europe | Component Speakers > KFC-W3011 (details)
Kenwood Electronics Europe | Amplifiers > KAC-9104D (details)

I quite like the sound quality at the moment but I'm sure I can get better =)

I'm currently in the progress of re-designing the boot in my car and am about to build a new sub enclosure to fit inside the spare wheel.

What the plan is so far:-
Get a fibreglass mould of the spare wheel.
Make another mould but of the sub woofer. This mould will have a circular wooden base.
Cut out a hole in the wooden base and put a aperiodic filter there.
Fix the sub mould into the centre the the wheel mould so there is a gap around the speaker.

I will try and find some 3d design software for mac or draw a picture and scan it in to explain better.

Just need to know, does this sound like a good plan?
Also, are the materials ok?
What wood should I use?
What's the best way to make a aperiodic filter? and materials?
How can I measure the impedance of the speaker to 'fine tune' the aperiodic filter?

I have done a bit of research, but I'm still a bit confused.

Thanks
JM