Now, about what Jax2 point out on " you need something very fast " we can read here something that help to understand that there is no such slow/fast sub performance device: forum.audiogon.com/cgi-bin/fr....
Interesting read! Thanks for the link, Raul. I frequently find myself stumbling for the right words, and am thirsty for better understanding in the things I enjoy. The article clarified some details for me, in this case - thanks. My recommendations still stand, of course, as far as standalone subs that might work well with Khorns. I used an ACI Titan with Klipsch LaScalas (which don't go nearly as low dropping steeply at just under 50hz) with some success.
I've also heard Duke's speakers at two shows now and his seamless integration of natural, detailed bass (going way down deep) in both those speaker systems was astoundingly good, and of the most memorable sounds at both shows specifically for that detail, as well as just plain great sounding systems featuring his speakers (RMAF & THE SHOW).
Stickman - I assume you are using the Khorn in corners, or false corners, as they are designed for. If that is not the case, that would be the first step I'd take.