I think grislybutter is right...
I bought a subwoofer years ago because my MIssion Cyrus never go down 45 hertz really...
With an organ music album it is a pity...
But the sub alone dont cure the problem and worsened it because the unbalance it created...I sold it on the spot... :)
I think it takes more than one sub to balance the system and the room...
Sadly at first but fortunately at last , my headphone replaced my dedicated room now because i sold my house... My headphone go so low under 30 hertz that i feel the wave with my body and feet by bones resonance and it is like the owgan was in my room... No sub is needed...And my new headphone beat my past speakers in their well tuned room..