smodtactical OPFor movie, theater and HT big 15" subs are great.
Are big subwoofers viable for 2 channel music?
But for 2ch hiend stereo system for music I find smaller faster drivers twin 8" or 10" are more precisely controlled and faster they mate up to your high quality mains better.
I use two active subs L & R, with twin servo 8" drivers in each, they are next to my mains, and get fed from the L & R outputs of the preamp, the system sounds like it's just designed as a whole.
Cheers George