Check out SV Subwoofers. Don't think you'll find any better value. Tom and Ron were very active in the DIY arena and various forums (you can read some of their contributions in the archives of HTT, HTF, and DTF. Follow the link in this thread: http://www.hometheatertalk.com/ubb/Forum1/HTML/000931.html
Subwoofer blues
I need help with narrowing down my sub woofer choice. I have $600.00 to spend and am not sure to buy used or new? My system consists of b&K AVP 1000, Citation 5.1, b&w dm620's and a nakamichi mb-10 using a x-dac. I listen to music but watch a lot of movies as well. I have listened to b&W and a few others but the bass seamed sloppy. PLEASE HELP Best regards Jim