Best subwoofer for a Wilson Puppy

Sorry, when I said "manual" set-up related to the Vel DD, I meant that there are no analog straps a la REL with which to override the digital display. One accesses the set-up utilities through display menus. If it is not possible to lower the xover point below an indicated 40Hz then you have a problem to discuss with Velodyne tech support.

It seems from reading many threads on Audiogon that outboard sub implementation is always frought with problems. Why not consider purchasing a pair of real full range speakers if you feel that last half octave is worthwhile? Rives has demonstrated that your speakers can reproduce below 30 hz. If you are in fact getting all of that now, there isn't much you are missing. Perhaps you need to consider whether or not your room is delivering all of what the WP-7 provides.
I have equalized bass from a full range speaker with audible signal below 20 hz. If I cut it off at 30 hz, I experience insignificant loss.

One further thought, I own a pair of Cabasse Saturn A21 subs which use a 1250 watt amp, provide for equalization and phase adjustment, etc. As this is a French company, it should be available in your market and is the best subwoofer that I have ever heard.

Macrojack, similar to the newer WPs, my Merlin VMXs are measureably flat +/-3db to 30Hz and produce usable bass down to 25Hz. Adding a sub below a low 30Hz crossover point adds significantly to impact of kick-drum, electric and acoustic bass, and expands the acoustic space for other instruments that unexpectedly reveal content well below 30Hz to a spectrum analyzer. It's also a nice dividend that at such a low crossover point, the transition from sub to mains can be smooth & unobstrusive, even moving from a hi-watt SS sub amp to a tube amp on top.

Since the human ear attenuates bass response as volume decreases, it's nice with a sub to be able to control volume & add a little boost as needed. Deep bass response of most rooms is tricky enough that being able to relocate the sub-bass woofer away from the main speakers can be an advantage. And all other things being equal, it's a lot cheaper to match a fine sub with fine limited low-frequency main speakers, than to acquire large-array full-range main speakers of comparable quality.

Finally, any additional tweaking required for a sub is a satisfyingly visceral exercise relative to wanking over power cords.

I'm interested in this as well as my WP7s are powered by 22WPC SETs. I originally considered switching to high current amplification but that would naturally compromise the SET magic.

How about the Kharma sub? Would this work well with the WP7s?