I think the "KGB" was a play on woords, rather than an actual circuit design Yellow_Light_Colorz_PDT_02
I'm not all that much into the deeper octaves and seismic wave generating "thump", but I did pick up a pair of the Dayton 10 inch, 100 Watt powered subs, back wghen they were on sale a few years ago.
http://www.bottlehead.com/loosep/S.E.Xy%20speakers.html
These are the same subs as noted on Doc Bottlehead's "SEXY speakers" which used Fostex FE-166Es in 0.25 cu foot sealed boxes, and then the subs to cover the low freqs, he suggested using one for each channel, as they were serving as powered woofers rather than "subs"" in his application. THese have individual level and "crossover" controls, and a choice of line level or speaker-level inputs. It's best not to use the built in "high pass" filters for the main speakers.
I ended up using those for TV and DVD usage, but they did sound pretty good for music applications. They don't deliver the 9.5 Richter Scale sonic booms that a 1000 watt, 15 inch powered sub will, buut then they are less likely to crack the foundations Yellow_Light_Colorz_PDT_04
Subs are one application where using Solid State (or Soiled State) is not a "sin" as the SS circuitry really does work better at the low end of the audio spectrum, and generating relatively high power levels is not too demanding.
/ed B[/i]