REL Subwoofer. Your input requested

Also have a pair of 212SE subs. Haven't quite dialed them in but getting closer. Have speakers with down firing subs in their base so in essence have 4 subs. The RELs have increased my enjoyment of my system. Can't compare them as they are my first subs, but don't have any desire to look at others. 

I had a T9i and now an S3 SHO and Rels are unique in their ease of integration and their finesse.  They are definitely a Sub bass system though.  
My only issue with both of the models I had, when using the Speakon connection, their is not enough control over volume level.  About 6 clicks from zero, there is not enough bass, 7 clicks and there is too much.  This is my only issue with Rels and it really is probably more of a mismatch between the model of Rel I was / am using with certain speakers.  For instance, I should be using 2 T5i or T7i subs with my Arro’s , not an S3....


I bought my S3 SHO as a floor model, no cables, missing grill for $1050 from Magnolia.  Came with warranty though!  They still have an S5 SHO for $1200 (no cables or grill) PM me if anyone wants it!

I should also add that in order to try to fix my volume mismatch issue I pulled the Rel out from the corner as much as I could without losing that deep deep bass ( the bass that you almost can’t hear but can feel... 25-30hz?) and also put screwed spikes into the footers to raise the sub.

I know from years of pro sound and home hifi abuses that a long run of unbalanced or RCA (low level inputs on RELs) cables results in funky signal loss and possible gum disease. I do wonder what if any effect there is on the signal from the use of long runs of the speaker output to the "High Level" input utilized by REL. I really have no idea what that might be, but it doesn’t seem to matter much...my longest REL run is maybe 12 feet of my home built Canare Star Quad wires (a very easy build for those considering it, and Speakon plugs are a joy to use), and gets the job done...somehow...

One other option you might want to consider is 2 x S812 SHO.
The 812 is the new upgraded S series that replaces the S5 SHO. It is stack-able with upgraded filters, and improved amplifier and diaphragm among other things.

If I were to upgrade my S5, this is probably the route I would take.
As good as the 212 is, you'll get more placement flexibility and I'd think a bit more performance in the end.