Okay here is the problem. You can't buy the box first then the subwoofers. You have to have the subwoofers to know how big the box needs to be.
For instance, with an X2 subwoofer you need 3 cubic feet for a ported box with 4 inch port. 1.35 cubic feet if you want a sealed box.
You build the box around the subwoofers! That box was only 49.00, that is way to cheap! MDF board is expensive carpet is expensive and the time to build it. On average I pay about 100.00 - 200.00 for my boxes. I have them custom built.
Also remeber this, I can give a person a subwoofer that will put out enough bass to drop 145dB and drive a girl crazy but if they put it in the wrong size box it will either sound like dog poo poo or it will cause the subwoofer ti rip apart, you put a subwoofer in the wrong type ported box and it can destroy the subwoofer quick.
Take your time in making your purchase this is a expensive habbit trust me. But it can be a lot of fun.
About that 10K watt subwoofer, I actual read about it in the paper where they did a huge review on it. Thats how I found MaAudio equipment, never turned back after that. I'll post a picture of the sub so you can see how big these things are. This is what I mean when I say look at the size of the magnet.
This is the 10K sub
Michael
This is an X2