Look at this PE flyer, page 23 top, a couple of good ones there
http://www.parts-express.com/salesflyer/index.html#22
maybe this one, or at least 2 for smooth freq response
http://www.parts-express.com/dayton-audio-15-ultimax-subwoofer-and-cabinet-package--300-7097
Then either a plate amp in each or drive both with an iNuke DSP amp
sale thread http://www.avsforum.com/t/1515340/inukes-on-sale
http://www.parts-express.com/salesflyer/index.html#22
maybe this one, or at least 2 for smooth freq response
http://www.parts-express.com/dayton-audio-15-ultimax-subwoofer-and-cabinet-package--300-7097
Then either a plate amp in each or drive both with an iNuke DSP amp
sale thread http://www.avsforum.com/t/1515340/inukes-on-sale