[Cash3481]

Hey Ben,
Here is a few things to think about in considering your box.
1. The woofers in post 1 are built out from the board and fiber glassed over to create a smooth transition.
2. If you add a skinny strip to the bottom of your box you can come farther out and not need as much buildout on the box.
3. If its 2" at the top and 6" at the bottom, that's a very small volume for the subs. I think you need to choose the woofers first then see what the requirement is for the tuning of your subs (how many hertz do you want the woofers to play their best).
4. Then get the total volume on each sub enclosure correct first then you will know how much is left for your amps and wiring section.
* Having the volume correct will make a lesser sub perform the best it can... while in contrast, having a better sub in the incorrect volume will make it perform worse than expected or at least up to its capabilities.
Good luck with your choices.