Subs?

Yes like many I recommend two subs or more if possible I listen to everything from Frank Sinatra too Odesza and I'm in my mid 70's I have two SVS Ultra 13 subs with the upgraded plate amps with DSP control My tower speakers also have built-in powered subs with gain control, so I'm assuming that it's like a bass array  All I know is when listen to my music I have no idea were the bass is coming from and trust me it sure can energize the room and l have the crossover set pretty low 

For sure not one sub.  It may make your system sound worse-it did for me. Two subs at a minimum, 4 being best.  As has been previously mentioned-the biggest effect of adding subs is how it cleans up the sonic clutter in your room. The second effect is a tighter more natural bass. The audiokinesis swarm is a great value and would likely work well with your speakers.  I had one in place for several years, until I realized my Magico S7's with 3 10" woofers each were running over the 4 10" subwoofers in the swarm. I switched to  4 B&W DB1D's and the improvement was astonishing.  If you don't go with the swarm, I would recommend that you chose a sub with DSP capabilities.  Again, at least 2 subs!

I'd have a good look at the Martin Logan BalancedForce 210, a pair of them.  They perform great and look just as good.  I really liked their older subs and I have owned them all.  I still have an old Grotto that I use daily in our family room system for TV/ movies and it's great.

@goducks44

Don’t waste your time with all these hoity-toity over priced underwhelming boxes... (2) 18" Eminence Tour Grade Subs powered by a Crown macrotech 2400 with a X-over, the rabbit hole is closed...game over.

Go Ducks! 🦆🦆

I'll throw in on this one...SVS makes a whole line of subs that rattle the rafters. They come with very thorough software application to help integrate into your system and if you choose correctly you'll find they offer very low distortion and enough headroom to satisfy anyone, especially if you intend to do multiple subs. They have a just recently released model in the 17" size that looks very impressive and according to what I have read about it sports the lowest distortion of any sub currently available that I am aware of. They are not cheap but I can say with confidence they are sure worth taking a listen to. They are readily available thru Crutchfield and other places too as well as direct from SVS. I have a couple of their smaller subs  in my music room and they do a fine job of filling in that bottom octave.