Your stated main speaker response isn't digging very deep so the sub will have to reach up a bit to cover the mains. This being the case, I would expect that a two sub setup will blend much better and produce fewer and less aggressive nodes. If your mains were rock solid down to 35hz one sub covering the bottom octave 20-40hz might get it done but that's not your reality. It would be ideal to get a dealer demo loaner to play with your existing sub to see how the pair works in your space. Good luck and cheers
Yet another Sub Question
Got a T/9x was considering adding another. But I think a remember reading on here someone saying they auditioned a Single S/510 vs 2 9x and chose a Single S/510. Seems like people always say 2 better than one even if you have to go smaller but....?
Feedback appreciated:
Room: 12 X 26
Current Tower Speaker specs
| Sensitivity (1W @ 1m) | 90db |
| Frequency response (+/-3dB) | 47Hz - 20kHz |
| Bass extension (-6dB) | 40Hz |
| Crossover frequency | 300Hz & 3.5kHz |