REL vs JL AUDIO

If I had to choose only between your two highlighted brands : REL

If I can select a best-of-breed choice that are true contenders and no pretenders : ATC or VANDERSTEEN

Between those two, I prefer JL.  My new favorite though is Perlisten.  I think they make a better sub than both as the DSP is best on market that I am aware of.  

IMHO...More is better, ie you're better off with multiple subs arranged to manage room modes than looking for 1 mega buck sub.  With multiple subs each one only carries a fraction of the load.

Oh no.....another "what's best" inquiry!

There is nothing special about the Perlisten subs, just marketing BS. None of them include a high pass filter, a fatal mistake.

I have also been turned away from JL Labs products due to multiple reports of liability problems. I have personal experience with one failure.

There are many fine subwoofer drivers out there now and many digital processors with fine bass management capability. The best way to deal with subs is to get a processor, separate amplifiers and passive subs. The key to low distortion is using large and multiple drivers keeping the excursions short. With bass management sealed subs are best. As long as you have the power you can make the sub do anything you want. 

You would be surprised how inexpensively this can be done. Parts Express has great subwoofer kits that anyone with two hands can build.
As an example; Four Dayton Ultimax 12 sub kits + a MiniDSP DDRC 22D + 2 QSC QX7 amps = $3400.00 plus some elbow grease. 
A single JL Labs Fathom 113 is $5000.00.