I don't see where that unit has the ability to roll off below a certain frequency to prevent driver damage. That is why the Behringer unit has been so popular with members. I would start to apply the subsonic filter at 25 Hz. Don't get too greedy.
That driver is really intended for a sealed application I think.
One thing you need to be aware of if you go sealed. That is a budget driver and a good sealed driver can not be made on the cheap.
Before Eq that driver is close to Xmax at 25 Hz. So when you add the Eq to extend the response 12 db per octave, the average level has to be lowered by 10 to 12 db to prevent driver bottoming and damage.
Since the db scale is log, the sealed enclosure will sound only half as loud as the ported. To have the same output as the ported, the driver would have to be able to handle 10 times the power, which it can't.
To make a really good sealed sub takes a very expensive driver with a huge xmax spec (over 40mm), and a driver voice coil than can handle kilowatts of power. That does not come cheap.
What this boils down to is that if resources are tight then you get much better value for money with a ported, TL or especially a horn design. However you need a bigger, box especially for the latter two. A horn sub for instance needs very little amp power. Matt 34 has just built one with a 12" Dayton sub, and he could drive it with a very small amp.
This occurs because in a sealed sub all the air movement has to be produced by the driver which is very inefficient in coupling to the air. Helmholtz resonators, pipes and horns are acoustic transformers, and radiate the LF from ports, pipe openings, and horn mouths much more efficiently than a driver cone, especially horns.
A sealed sub requires a "brute force and ignorance" approach so to speak, however that does not mean to say that given enough resources they can't sound very good.
