I would tend to stay away from them...
Simple reasoning, Spec's and appearance are way to close to a certain pyramid subwoofer on the market. (Hyper-Pro, I believe)
Take a look in particular at the basket and motor structure of the woofer- both the Visonik and Pyramid models-exactly the same. While many manufacturers frequently do "parts swap," only so much can change in the form of T/S parameters when you have the same constants in design.
Really, it appears that Volfenhag simply added an aluminum cone to the works and said good to go.
With that and the similar specs in mind, not to mention, the volfenhags distasteful use of color, I would tend to steer clear of these speakers.
I'll locate some pic's of each model and throw them up here so you can see the similarities also.
I have came across this question a few times, so I will locate the info from an old post of mine where everything is clear.
-take it easy,
-zane