Your sub experience: Easy or hard?

Easiest and most significant impact to SQ, to date. Started with a single REL Carbon Special. Returned it because I had to keep adjusting the gain. I could not find a one size fits all setting for my exacting taste. I tried a REL 212SX next and I barely had to touch the crossover and gain controls. It was dialed-in within a few diverse tracks. Now I own a pair of 212SX and will never live without subs again. I have towed one of my 212s to audiophile friend’s homes and blew them away with the improved mids and overall depth of stage. These are friends with Wilson Sasha DAW, Dynaudio Confidence 60 and Focal Scala Utopia EVO. Subs were a definitive lesson for me and my circle. I saved a ton of money and chose a smaller main speaker there is no argument I am missing anything compared to any other system I’ve heard with speakers costing way more than my subs and mains combined. If you did not hear it above, a single 212 was basically plug and play. No joke. A pair are heaven in my room.

Moderate: Stereo pair, locate near mains, phase 0. Took some time and effort listening to a variety of music to get the gain and crossover dialed in. 

Easy. This system was easier the previous. Full range towers are way easier then standmounts. Just filling in the low low. I listen to lots of bass heavy music and the sub is a must. RTJ3 on vinyl as I write this. The sub disappears. Blends seamlessly and provides a more visceral experience at low listening levels. Took 30 minutes to find the correct placement and another few listening sessions to pin down the crossover and level. Easy peezy.

REL subwoofers are different.  Their high-level connection allows them to play more as woofers.  You also need to add a pair and at least start with their SHO series.  Then make sure not to play them with over a 40% volume and dial things in to make sure they blend in.  Bass fall off with volume and you will notice is you are able to play you system with lower volumes and still hear bass.

We can assemble the modules of the ISS built in different countries and assembled in space with success. We can have a “relationship” through AI. We can pinpoint and “paint” targets for invisible air strikes. 
Why in the heck can’t someone figure out an intelligent sub that can adjust volume as needed per recording?