Grotto i subwoofer
I recently just acquired the Grotto i (actually two of them) for my stereo only system. In the past I had the Sunfire, the Sunfire was fast and powerful, but in my room I always knew it was there (mk2 version).
I got the Grotto i's about a week apart, when I had only one I installed it in between my speakers and was very impressed; it's fast, clean, tight and depending on how it's adjusted...disappears!
A week later the second Grotto i arrived and I now positioned each sub next to a main speaker (Acoustic Zen Adagios).
Was there a difference...yes!
Don't let anyone ever tell you low frequencies are not directional, once you hear two subs....you'll know!
Can you live with just one, certainly, but it has been my experience that sub placement will draw your attention to that spot when lone bass notes are played.
My room is 26x14x8 and I'm still experimenting with short/long wall placement.
However, I heartily recommend you pick up that grotto i....now!