I own two of those subs with my Canton 9k reference stand mounted speakers. I started with one SVS sub which added the needed lower frequencies, some time later after reading about the benifits of two I got a second sub for my12x16 room They are dialed in at their lowest setting to fit seeemesly with my Cantons any thing above that setting and the base overpowers the cantons and the room.It looks better however, lol .My recommendation buy just one, buy a second one if not satisfied. The second sub will be a positive addition but not a Wow difference, not in my room oh I'm not an anal Audio guy so I did not get excited over the addition, just yea I hear some positive improvement here and there and in total the speaker system sounds great.
PS If I turn up the subs to their max I can't hear the other speakers and my house starts to move off it's foundation.If I had to do it over I would as I have the disposable income to otherwise not sure it is wort it in the short run cost benifit wise. Yea I know I speak blasphemy.your speakers and room are different then mine soooo there that.