I am still confused. Do you recommend subs for 2 Pi Towers? If so, what do I need to consider if I wish to add a sub (or subs) to my system? This whole speaker/crossover/sub thing is rather new to me. While I could build a set of cabinets from you basic plans for my speakers, I am not able to intoduce subs without some more information. If you prefer, I can contact you by email. Thanks.