No.
For $700, you can do MUCH better than a Def Tech sub. The SuperCubes are a neat way to get quite a bit of output from a very small box, but they are a heavily compromised design. If you absolutely must have as small a subwoofer as possible, then fine, you deal with the compromises in performance. But if size is not your paramount factor, there are much better choices for the same price.
An SVSound PC12-NSD DSP cylinder sub would be an upgrade to what you already have. Keep in mind though that two subwoofers usually offer the ability to provide more even bass response at multiple seating locations - provided you can place both subs optimally. That said, the single SVSound PC12-NSD DSP will play lower, louder and with better delineation and transients than your current subwoofers. It just can't do anything about being a single subwoofer and not dual subwoofers
The HSU Research VTF-3 MK3 would also be a significant upgrade for the same price. I would favor the SVSound's performance, but if you hate the cylinder shape, the HSU VTF-3 MK3 offers fairly similar performance in a big box shape instead.
