Hey holmz,
I'm pretty knowledgeable, but first to admit I am not a designer or electrical/acoustic engineer. With your concerns/questions about band pass active subwoofer design I recommend you give a call to Erol to discuss. I'll also ask him if he would want to put something on this thread addressing your questions.
Based on my experience, ported, acoustic suspension, or infinite baffle subwoofers (have had highly regarded and very expensive models in-house for review) come no where close to the natural pressureization of my room delivering a spatial presentation that is a more accurate illusion of live music. Secondly, the blending of the upper bass frequencies with the lower midrange is more seem-less giving the "power range" foundation that allows a system to have a sense of authority/control.
Teajay (Terry London)