REL Vs SVS for 2 channel music listening

I believe I have them dialed in about the best a single sub can do for my space. I am going to purchase a second in january/ I have it to where sound seems to lean to 53% left and 47% right (placed behind left speaker.). I set up with mono sources. Really, I could live with it. I would say a general listener would not notice.

I'm amazed how the sub really adds a presence to listening. For my taste, the bass should sound cozy and warm. The sub adds that along with some punch. You can really feel Neil Pearts bass drum and the moog bass pedal on Moving Pictures by RUSH. The heartbeat on Dark Side of the moon has a little tiny bit of stomp to it (which i like). For now I have it dialed in. I may do some more changing later on...but I really like the results thus far 

I added an REL S5 about a year ago to my Tidal Contriva Diacera SE speakers and that really improved the room bass but then I recently added an REL 212 SE ....and kept the S5 for the lt side of the room and now the whole presentation is magical.i will,at some point,replace the S5 with another 212SE but for now, all is great.one of the REL VPs came over to help with the room positioning which save me a great deal of trial and error.

I have an older REL R 305 and its a nice sub.  I auditioned new speakers recently and paired it with an SVS and it was no slouch 

Calloway... 
I have an S5 as well, and chose it over the 212 SE.
1. Recently I've been wondering how much I am missing with the S5 vs the 212 SE.
2. I'm thinking one of the upgrades this year is dual subs, similar to yours. 

Thank you in advance for any response... 

Calloway how do you you have your RELs connected through Neutrik? Which REL is connected to what speakers and where do you have them placed?