I'm still waiting for someone to post a case where they have added a remote DSB bucket and had there nitrate drop from a significant number (>40 ppm) to a low number (<5 ppm). This is surprising for such a huge thread with so many contributors.
Some have posted that there nitrate is zero, but none have attributed it directly to the remote DSB bucket. The only example was at the beginning of the thread where Anthony Calfo described a 55 gallon tank filled with sand at a LFS. He didn't give all of the details of the tank. It may have been recently set-up, or it may have been in the hands of a typical LFS staff, so I don't know how qualified the endorsement is.
Several people, including myself, have asked this question throughout the thread, but no one has come forward yet. I am a firm believer in DSB use for nitrate reduction, but most of this is based on theory, not empirical data. Proving DSB's work is a relatively easy task with tangible scientific evidence behind it. Proving the quantity and configuration of the sand is another matter entirely.
The most significant DSB study I know of is the one by Bob Toonen, but it has its' limitations.
http://www.advancedaquarist.com/2005/6/aafeature