In response to your comment, I may be on a different branch of the right track rather than on the wrong track. As Jim points out, equalization can compensate for the bass rolloff of low QTS drivers in open baffle designs (and in sealed enclosures too), giving you the gift of extended bass response without the group delay and other disadvantages of a ported box. Good idea if you're using multiple high quality woofers, like those in the Orion, that can handle the extra power needed to drive them at low frequencies.

I was looking at some drivers in WinISD, using a 1,000 sq ft "sealed" box to mimic an open baffle. The Eminence Delta 15LF, with a .58 QTS has an F3 of about 51hz - not too bad. The Silver Iris, with its .98 QTS is an even better candidate. Its bass rolloff begins at a much lower frequency than the Delta LF, which would provide more midbass punch, and its F3 is about 35hz. So now I'm beginning to understand why hurdy gurdyman is so enthusiastic about the Silver Iris driver.