SVS or REVEL Subwoofer

I do support the REL T/9x given your original posted budget.  When you go up the line, subs will generally dig deeper with clarity.  Good brands, up the line, will have better constructed drivers, more inert cabinets and more power.  You have excellent speakers and really just need to augment the bottom octave.  In real world use this I see it as the 25-50hz range.  The T/9x will do this and the S/510 will do it better.  The S/510 will roll off lower and give your system more weight.  It would be unfair of me to speak about the B&W sub since I've not heard it.

When you meet with your dealer, make sure they are familiar with your room.  If they haven't see your room, bring some pictures to share.  Also, be sure to talk about the structure of the floor and what's below it.  This is important to how the sub will play in the space.  Good luck and cheers

@2psyop Thanks for the heads up on Nemo Propaganda for sure.

@rick_n Thank you for your feedback.  I'm going to give the REL T/9x's a good listen tomorrow.  Same with the S/510's.  Given the magnitude of the discount the B&W DB2D's (retail $4,499.00), I will give them a serious listen too.

Listening to music now without any sub and I'm just, depressed.  LOL. 😐

@2psyop I watch the video tonight.  Impressive.  Now I'm leaning toward the HT/1510, I think.  Or maybe the T/9x . . . ?

rick_n offers sound advice.

Let your dealer help you without bullying you. Giving him/her the measurements of your room, treatments, type of equipment you have, tastes, stereo vs HT listening, etc. They are the most experienced at these kinds of decisions. And if he/she is a GOOD dealer, you will be allowed to test drive any unit in your home. Don’t forget to ask which brand will back up service and support the best. That can be a crucial consideration that many audiophiles overlook. Also Nemo Propaganda does comparison videos which are also informative. Ultimately it's your call... good luck.

SVS is primarily sold directly from the manufacturer. They can easily be adjusted and or positioned to sound less desirable than a REL.

The REL is a -6dB sub-bass speaker equipped with only basic crossover, 2 position phase switch and volume. Because its low frequency roll off is so dramatic it simply does't excite a rooms standing wave modes and can be located most anywhere and often next to the speakers.  

The SVS is an actual -3dB DSP equipped subwoofer. If its not located in the rooms standing wave mode it can over excite the rooms modes and possibly sound boomy. If the SVS is demonstrated in line with the speaker and the REL its likely out of its optimum position in a null. DSP is not intended as panacea for null or poor positioning rather to better match a speakers low frequency presentation.

If this looks to be the case and you find the REL to be more appealing to you, I'd suggest a dealer is pissing on your shoes.