This is the review I was looking forward to most of all. I was wondering how a "commercial/DIY" (I know - kinda oxymoronic) sub would compare to the purely commercial offerings. It certainly held its own! But, the same issues that us DIYers face must also be addressed with the FW 12.X.
Using external professional amplification usually requires conversion from balanced to unbalanced connections. This can lead to ground loop problems, if I'm not mistaken, although I was fortunate enough not to encounter this. And, with the power demands of this model, a separate power circuit could also contribute to ground loop issues.
There's the fan noise (I solved my fan noise issue by putting the amp in a separate room).
Then, there's subsonic filtration (of course, that requirement depends on how hard you push the sub).
I think this is a great subwoofer. However, in it's current form, it will remain a niche product, confined to those who can't/won't do cabinetry.