I can't speak to which series is better for your application, although I would say the B series is a better quality sub, and better suited for pure audio appications, and the R series is better suited for home theater.
However, if I understand your plan A correctly, your 15' x 17' room will have a total of 3 subwoofers? If that is correct, I think that's big-time overkill. Two high quality subwoofers in that room will be fine for home theater. I'd focus on the quality of the sub(s) you purchase... not quantity of subwoofers. More is not always better.
However, if I understand your plan A correctly, your 15' x 17' room will have a total of 3 subwoofers? If that is correct, I think that's big-time overkill. Two high quality subwoofers in that room will be fine for home theater. I'd focus on the quality of the sub(s) you purchase... not quantity of subwoofers. More is not always better.