HT Subwoofer build ideas/question

I'm looking to save a few bucks and have a fun project to do all at the same time.

Here's what I've come up with so far.

Company called Elemental designs sells a custom built subwoofer for $1300 plus shipping. :bigeyes:

Interal parts are

1300 watt plate amp = $350

18" subwoofer = $195 (I would think dual 4 ohm is what I need?)

Total = $545

The box 25x37x25 (ported)

Any ideas to help me build the box? This is what their $1300 box looks like. Anyone here make a box similar? Do I just use PVC for the port tubes? Thanks for any help ahead of time. :)

Yeah... here is a pic I snagged off another forum of the finished product.