Subwoofer advice sought

Your Totems already reach down to 28HZ
What you need is impressive depth below that.

I researched subwoofers for over a year before buying.
What I learned was one big powerful cone is better than multiple small cones or passive radiators.
If I were buying now this one goes to 17hz or so they say.
Even if only practically 20hz... MUCH more oomph than the two referenced above.
https://www.svsound.com/products/pb-2000
Generally speaking you need a 12" cone to get to 20hz.
Listen to the attached video !

BTW I ended up going over the top with this;
https://hometheaterreview.com/definitive-technology-trinity-subwoofer-reviewed/
One of the best subwoofers ever.
Earth shaking in movies (literally) yet clean and pure for music.

Its just fun to watch peoples jaws drop ;)

Just adding in.  DBA setups do have the potential to give extraordinary bass.  If you have the money and ability to implement 4+ subwoofers in a sealed room with proper inverting cables or circuitry for the rear subwoofers, then go for it!  If you just want to beef up the bass/sub-bass on your Totems, then getting a nice single subwoofer is like a better choice.

I have heard Rel subwoofers.  They are nice and clean and have very good tonal definition down in the bass area.  Extremely clean.  But they are not powerful and meaty sounding subs.  If you want more of a meaty and gritty audiophile sub, I would look first at Rythmik ported subs.  There are others, such as Hsu and SVS.  SVS has a distinct tone that is popular with consumers of Best Buy, but it's kind of a one-note-wonder and doesn't have good resolution (in my opinion). 

The "subwoofer output" on your integrated is likely just a full range output.  I don't see any mention of a crossover inside and there are only 2 tubes.  The Vandersteen is an option if you want a try crossed over subs that blocks all bass from your main speakers.  The Rythmik would be if you were fine driving your Totems "full range" and just wanted a sub to fill in the missing sub-bass area.

I don't often see 4-6 double bass players scattered throughout the venue to immerse you in their bass.

If you've ever been to a rock concert or especially an EDM show, the bass travels throughout the venue and you feel it as much as hear it.  That's one of the great things about having multiple subs is that it feels like live music.  I don't recall ever hearing the bass only coming from the direction of the stage at a live concert.  Of course it's been a while since I've been to a show, perhaps my memory is playing tricks on me.

@big_greg  You're exactly right...the bass is traveling throughout the venue even if it's originating from one side of the stage.  This is the effect of the venue or the room.  What you are experiencing is the room effect on bass.  They aren't creating it at the concert by putting bass signals in an array throughout.  You have a room as well that you listen to music within.  Look, I totally understand why a DBA would work and help counter the effects of uneven bass distribution in your room.  My point is that this technique is dealing with room acoustics and the whole point isn't to place the listener inside or "enveloped" within the soundstage. But like everything else, just pick what you enjoy listening to most and the way you enjoy it implemented most.  There is no wrong way.  

@three_easy_payments We're in total agreement that there's more than one way to get good bass and that different people will enjoy different things.  I've enjoyed good bass in my system with no subwoofers.  I have three other systems that all have one subwoofer.  One of the best systems I've heard had two subwoofers.

Using four subwoofers, I don't feel like the bass is enveloping in a surround sound way.  The soundstage is still very well defined, perhaps even better defined.  The performers are there in front of me, including the bass player.  If I'm listening to Yes for example, I can tell exactly where Chris Squire's bass is coming from.  It's not in surround sound, it's coming from a specific spot on the stage in front of me.  The sound fills my room though in a way that is the closest thing I've felt to live music in my system.  And yes, I enjoy it very much.

I'm not sure my words are adequate to describe the distinction between the surround type "3-D" listening experience you seem to think is created and what I experience.  Have you experienced a system with multiple subwoofers?