I've had subs for years and can share my experiences and 'growth' as it may be; For many years I have had several M&K subs, They were the sh## in their day, dual 12" push pull, very articulate but not the absolute 'deepest'. But what I quickly learned, was that two stereo subs, each being fed by distinct left and right inputs if possible, was way better than one sub, no matter how great it is. +1 to noble100 on that. (and I am sure that 4 in an array is the best but that is not going to happen for me). Anyone that says you can not localize where a sub is is just wrong or can't hear. I can sit right in the center with one sub blindfolded with mittens and tell you where the sub is, even when adjusted well. So two is the bomb. About two years ago I got a paradigm studio 15 new on a great clearance. Wow. Deep and low. but just one...(the M&K's are now gone). So I got another and had stereo 15' paradigm's, pretty nice.
But the lady thought they were hideous, and I was able to use them downstairs, so I started researching Rel. Now I feel I have grown up about bass and subwoofers. I now have stereo REL Carbon Limited's.
It is not about just hearing and feeling the deep stuff, but it about how they pressurize the room and support the stereo imaging and sound of my Revel Studio 2's. I have a large room, all open from family through eat in area to kitchen. So a lot of air. The sub's you ask about are also awesome, but it is about how the REL's feed their input off of the amplifier to receive the 'exact same timing etc' to keep everything sweet.
I also use the Longbow wireless and it works easily and perfectly.
And get this, the lady thinks these REL subs look good! Read everything on the REL site before you purchase anything. The Rel SHO 5's would have worked but what the hell...and you can find discounts on new REL subs.