Thank you guys for your inputs...the technical (Uncle Dave, B2 and Luis) and the humourous one (by freddynl)! I'm leaning towards getting a small powered sub that is easy to carry and won't take up much space. I can sacrifice some "air movement", as Uncle Dave explains it. I just want to be able to hear (and feel a little bit of the) bottom end. Luis, I could not find any US distributor for the Montarbo subs.
I'm still be looking...Thanks again, folks.