FWIW, I've done a bit of research as I want to move beyond my 4 JL Audio Reference - class Fathom subs. Rel, JL Audio and most other cones in an MDF box (or MDF - like box) fall into the same category and can be very good, or not IME.
Then there are the more exotic / extreme cones in a box such as Wilson Benesch, YG, Magico, etc. that I'm sure are a half step - a step above the aforementioned wood box subs.
Out of both categories and subs above (and almost all other subs including the Pre Low you mentioned), the one design area that always concerned me was - nothing is done to manage the driver's rear output which causes smearing. Vivid Audio mitigates most effectively, btw. Other than OB which have their own challenges (e.g.: lack of efficiency), I know of only two companies that "manage" the driver's back wave and its associated distortion - M&K and Perlisten. However. Perlisten is like M&K on steroids in terms of cabinet and driver engineering and construction and microprocessor capability. In a push - pull configuration, even order harmonic distortions are greatly reduced. That, coupled with intelligence that manages driver output to ensure uber - low distortion makes for one of the very best subwoofers Audioholics has ever measured and reviewed.
Net is - After significant time hearing and researching subwoofers and having now heard the top reference Perlisten sub, the S215S, I bought one, excited to get it set up in the next few days.