Are big subwoofers viable for 2 channel music?

I have not experimented with the SWARM concept but did hear Duke's room at an RMAF (remember when we used to have those :-) a few years back an he definitely had good sound and balanced low end.. I have experimented with subs for two-channel music and surround as I have those two formats integrated into my current main system.  What is current working for me is a pair of Seaton Submersives (active dual opposed 15 inch drivers). They do not have any form of crossover for the model I have. I use a DBX PA-2 drive rack which is a DSP that I use for he low pass crossover (many choices of crossover type), PEQ and RTA.  I run my main speakers fully range and bring on the subs where they start falling off. I use an RTA app on my iphone that gives me 1/3 octave RTA measurements. The DBX PA-II has an iPad app so you can control all the settings remotely. It also has a large number of user configurable presets..so I can have a setting for each speaker I might bring into the system.   The cool thing is you can play with all these settings easily from the listening postion. I stream a pink noise track, look at the RTA on my iphone and play around with crossover points, slopes, gains, etc while
I am listening.. I like to play around with the crossover slope types while playing music with real bass (like Dire Straits - Six Blade Knife) and listen to the impact of making changes.  Do I end up with something that is perfect....no., but I do end up with something I like.  I also strongly agree that subs is not just about adding bass it can transform the spatial aspects of a performance.   For surround I have an XLR switch box going to the two subs...so in surround mode Iet the Surround Pre control all aspects of the subs by routing around the DBX PA2