Apparently the Definitive Supercubes rely heavily on room gain and positioning. I'm tampering with a small Yamaha subwoofer with an 8" woofer using the positioning methodology suggested for the Supercubes and the results are good for music, blending is pretty seamless.
I also have a Klipsch Sub10 which is on the large side. It's rear ported and has a large cabinet volume for a 10" subwoofer. It is positioned between my entertainment center and the right front speaker. I placed the Yamaha behind the front right speaker (front right speaker is about 3 feet away from the back wall and 1 foot away from the side wall, not much I can do about that).
So far it seems the Yamaha integrates better but obviously won't share the Klipsch Sub10s ability to produce strong LFE for movies. This brings me to the Supercube. The Supercube should successfully replace both subs giving me the best of both. The size and punch of the Yamaha will likely be bested by the Supercube and I suspect it will also out the Klipsch for output and extension (the Sub10 is only rated down to 25Hz I believe and even with room gain it doesn't go much lower, maybe that's because of it's own cabinet volume and port tuning?).
I've read in several places that the Supercube II is capable of causing structural damage. While this isn't necessarily a positive thing I like to know it has room to expand if I need it to.
One user review had indicated they had previous experience with a Miller & Kreisel MX-70, which is what is very similar in design to the push-pull MX-100 I used to own. The MX-100 remains my favorite sounding subwoofer that I have OWNED, but it died long ago and I left it in the wrong hands for repairs and now it is gone. It had exeptional depth and accuracy, but had limited output due to it's meager 100 watt amplifier.
Having heard the Supercube II in the showroom I can certainly understand where the reviewer had come to that conclusion. I've heard the Supercubes under good and bad conditions and placement with this little gadget is absolutely the key to getting them to sound amazing.
I'm keeping my eyes peeled for USED subs, so I'm hoping to nail one for a good price. I'm watching all active listings and constantly checking for new ones coming up for sale. I've got the deal finding down to near science. If I can get either the Supercube I or II for $400-500 respectively, then I'm probably going to get one. I can offload the Klipsch and two M&K single 12" sealed cabinet subwoofers I'm not using, and just keep the Yamaha because it's not worth anything more than $30 on the open market anyway.