Play with the HI/LO level adjustment...1 click at a time. I can quickly fill my room with more bass than my neighbors can stand with 1 S5 SHO. It does take some time and tweaking to get it dialed in but the results are worth it.
The problem is that I'm only connecting the LFE input to the sub from the Anthem receiver, so there's really only one adjustment and that's the LFE volume.
I've been working on this off and on since I originally posted this, and I've gotten nowhere. I called the shop I bought them from and asked if they thought trading them both in for one S812 would help and he said probably not. He thinks it's something with the Anthem setup that's not delivering full power to the REL.
I don't doubt that, but I've poured over the Anthem setup and can't find anything that I haven't tried already. I turned ARC off/on, changed the crossover point...nothing changes the bass level. I should be getting blow away with the LFE volume cranked to the max...but just very OK HT bass.
Not sure where else to go cuz my 2 channel sounds amazing with the REL sub!