I would have to agree quality over quantity anyday. Now let me get this straight your putting 2 8s 1 10 and 1 12 in your hatch? You do realize that you have to have a certain amount of airspace behind the sub for it to sound good and crisp.
Building your own subwoofer box
An enclosure does more than simply hold the woofer; it is an integral part of the system. A properly sized and built enclosure can turn an inexpensive woofer into a good performer, while a poorly designed or constructed enclosure will make even the finest woofer sound like mud.There are two main challenges in fabricating an enclosure — making sure it contains the proper volume of air, and controlling the cabinet resonances that otherwise will compete with the sound from the woofer and color its sound.
The ideal volume of an enclosure (length x width x height) will vary depending upon the woofer you select. The enclosure volume for your woofer is usually quoted as internal volume. Therefore, in calculating the overall external dimensions of the box, you must take into account the thickness of the board, the space occupied by the speaker and any internal bracing.
Once you know the internal volume you want to achieve, you'll decide on the dimensions of the enclosure. As a rule of thumb, make sure no internal dimension measures more than three times that of any other. But don't make them too close to each other or you will have a cube &mdash one of the worst acoustic shapes for a speaker.
Finally, determine whether your box will be sealed or ported. A sealed box is the easiest to design and build, and protects the woofer against subsonic bass that can affect its performance. A ported box uses a tube (port) that reinforces the bass produced by the woofer. It can offer excellent, high-output performance, but is more challenging to construct.
For more on the topic, check out our article How to Build A Subwoofer Box.
http://www.crutchfield.com/learn/learningcenter/car/subwoofer_installation_guide.html?page=6
But, Id say get a nice alarm system, and tint your windows.