@highend64 I started with 1 REL T/9x and then went to a stereo pair. I don’t think you will necessarily get louder base, instead you get more of what you already hear.
Try unplugging your REL and mane sure your main speakers are in the best location to get to most articulate, fast and musical base possible. Then add in your 1 REL using the crawl method. Very small movements of the REL can make a big difference. For me, pointing the REL from near one corner, firing across the room to the other corner, was the sweet spot…..not placing the REL next to my main speakers “along the same plane.”
Then add a second REL to enjoy to immense benefits of a stereo pair.
By the way, I have a small room and use the high level connection with RELs upgraded Speakon cable.
hope this helps!