You might to look at the following article which talks about how to maximize the use of subwoofers (both number and placement)
www.harman.com/wp/pdf/multisubs.pdf
www.harman.com/wp/pdf/multisubs.pdf
Two Subs Vs. One
Trying to augment the sound from a pair of Totem Hawks in a large room (rest of system is an Olive Musica server, Eastern Electric Minimax Pre, Classe CAP-150 Amp). I am doing some in-home auditions of affordable single subs (mostly REL) and really like what they do for the sound. So far, I am leaning toward two smaller subs, one behind each speaker (ie. REL Q108E's - I like the sound better in that position and it looks better - wife factor) versus one larger one in the corner (ie. REL R-205). Can't find two demo units of the same sub to audition the two-sub option and was wondering if anyone had experience with this comparison.