Hey ryder,
Not sure if this is the kind of information that you are looking for. In my system I am currently using 2) SVS SB4ooo's, 1) Rythmik F12SE and 1) REL S5 SHO (predecessor to the S812). In my opinion the Rythmik has a slightly better sound than the SVS and both of them are better than the REL. I had to slightly modify the REL in order for it to compete with the other two. Both the SVS and the REL have more output power than the Rythmik. The SVS was easiest to integrate due to its phone app. The Rythmik was a little more cumbersome because you had to make the adjustments at the cabinet and not the listening position and REL does not give you enough tools to properly integrate so I had to slightly compromise the integration of the SVS and the Rythmik to work with the REL. Overall I prefer the Rythmik, but I would move up at least one model size larger if not two, in order to compensate for the lower output power.