The subwoofer driver used is the Stereo Integrity HT18: http://stereointegrity.com/index.php?id=60 Currently they have a preorder set at $162 for the next production run of those drivers since the first round was so popular and sold out quickly. Price goes up to $175 after the preorder.
The enclosures were custom built, I used 9 4'x4' sheets of 1/2" plywood to construct them. Total materials cost for both enclosures came out to right about $300 but the grills alone were $100 of that. The grills where ordered from Reliable Hardware