As it’s been said, two is better than one. Being a bass head I finally broke down and implemented a (DEBRA) four subwoofer system and the improvement is remarkable. An immersive experience, better imaging, not just more bass but a new window into recordings. I will never go back to a single or dual sub setup. There’s lots of online information on setting up multi-sub systems or you could purchase an AudioKinesis Swarm.
Dual Subwoofers?
How about the idea of a separate subwoofer for each channel, using passthrough to bookshelf speakers. What say you?