[GMo]

I like the tempest in a larger box, as your HT setup is.
I find if the Qtc isn't low enough, the bass is too pronounced, (less tight sound, but greater amplitude) probably due to a lack of dampening around resonance causing a very noticeable peak. So for the temnpest I would prefer a slightly over damped design.
As you go lower with your Qtc goal, I would say tightness would increase, and amplitude would decrease, but that's probably what you mean and we are saying it differently.

 

[GMo]

With a box that large sealed would have low bass response as well.
I think npdang, like usual, hit it right on the head with eq'ing it regardless of enclosure.
But my preference is in line with you going to a larger box for that driver.