What a coincidence, I just heard from one other party that my Linn dealer tried the combination of the Akubarik with a subwoofer. It turned out finding a matching subwoofer is quite tricky since the amplifiers do not match with the LINN Exakt system. However, the combination with the Wilson Benesch torus, a subwoofer with separate amplifier, seemed to work. So I decided to hear this combination and drove to Erlangen. The system consisted of the Klimax System Hub, Akubariks Katalyst, a sub Exakt box connected to a Klimax Twin driving the torus, and was already running. The sound was natural, and the torus was well integrated. We listened to Beethoven's six symphony. The base was more pronounced without destroying the ensemble. It just added the missing part. Once the subwoofer was switched off, this became even more obvious. After some genre changes showing always the benefit of the torus to the system, we decided to replace the Klimax twin with an Akurate amplifier. Unfortunately, this combination did not meet the previous one. In fact, I thought that the sound did not benefit from the subwoofer at all. We discussed other subwoofers as well, but my dealer said that they would not match the speed of the Akubariks.
In summary, there is some evidence that the Akubariks benefit from the Wilson Bensch torus subwoofer. Still, the amplifier is critical, requiring the top-end of the Linn system range. I think if you own the Akubariks Katalyst, you should definitively try the combination with a subwoofer.