Subwoofer Choice Question SVS, Majico, JL Audio, REL

low325, FYI, Devilles were props in, I believe, the first episode of "Just Like That." 

We managed to get much better performance from a down firing REL Studio III by locating it on its side in the rooms major mode and using L&R processed low level signal from an early remote controlled Velodyne DD. While this improved its presentation noticeably it didn't equal the, at less than half the price Velodyne and its low frequency response never reached the manufacturers claim. 

I have owned the fathom 113v2 with CR1 and the S510s. The companies obviously different philosophies. While JL's features are all about the frequency response, REL has videos suggesting positioning by way of impulse/timing in reference to the main speakers. That would be impossible with the fathoms. I am confused by REL's approach. Positioning subs to sync an impulse with main speaker would realistically mean the frequency response will not be optimal. Like Duke says, my experience is that peaks and dips and long decays are easily heard and measured.  Their difference are also reflected in preferred connectivity. With my (balanced) amp, I much prefer the ease of low level inputs to the quirkiness of hi-level used by REL. 

The fully automatic EQ included with the fathoms is powerful and does allow for  more liberal placement than the RELs. I. did have personal satisfaction of getting the mains and rels just so, to even out 40Hz and below, though. Ultimately I needed a crossover to flatten a 60Hz vertical resonance from my main speakers.

It is hard to know what features are needed for both particular people and particular rooms/speakers. 

Duke is being much too modest (as usual):

@m-db thanks for that bit of info on the tv show. I will have to check it out.

regarding the fleetwoods - they are solid. Just not bass impact performers in the 80hz - 100hz region. I want to hear that slap or impact here.  No one said they were but I crave this for me and the type of music I listen to  

regarding my carbon specials. I am asking them to do too much especially if I’m not willing to tune or walk them around the room as they should. Due to their size they have to stay visually appealing. I’ve used rew and I do get down pretty low but I have room boom and without some sort of eq or more room treatment the subs will just overpower.

I have personal experience with REL, SVS, Rythmik and to a much lesser extent Martin-Logan. In my experience Rythmik has the best sound quality, though not by much, but if you have  a penchant for loud bass heavy music, they may not have the power you would need for them to keep up. SVS in my opinion is a great value and should be able to handle anything that you throw at it. REL sounds okay but is just not worth their price. Unless you need the auto correction, I would look at the "E" series instead of the Fathom. Magico, I have absolutely no experience but they seem like an awful lot of money for probably very little if any audible improvement. I would definitley want to do an AB comparison before I bought them.

Of all the subs that you have listed, I would pick the SVS.