I’m a big fan of SVS SB-16 Ultras, I also have two Kinergetics SW-800 subs which I bought used and it took five years to find them. I ageee with a lot of posts above. Four asymmetricaly placed subs are best, use an active crossover such as a Mini DSP (Can add up to 12 biquad crossovers on each channel) with REW (Room EQ Wizard) to measure the room and MSO (Multi Sub Optimizer) to build the crossovers and you’ll have musical bliss. Money has to be spent to get low frequency control and tuneful base. I’ve spent almost as much money on my subs as my main speakers. I can’t emphasize enough the importance of the active system. With four subs phase, time delay, and room nodes can be corrected, which is the one note base people speak of.
Thanks,
Steve