Unfortunately, the subwoofer tests on AVTalk.com seem to have gone dark.
IIRC, those tests showed that none of the products you mention are actual
SUBwoofers. They are (very fine)woofers whose performance starts to fall
apart below app 50hz or so (at 100db levels). This is probably adequate for
most musical sources.
However, if you want better extention, you might want to consider the
Rythmik audio subs (I just bought a pair, but haven't set 'em up yet.) They test
a lot like the RELs and MJ, but down to app 35hz. Below that, they start
encountering trouble. The JL subs get a little more extention and the SVS a
little more than that. However, neither the JL nor the SVS test quite as
"fast/tight" as the REL/MJ/Rythmiks.
Bear in mind, these comments are based on test results - not listening tests
(though I've heard REL extensively and own Velodynes). Take them with that
grain of salt.
BTW, the sub tests at HTshack.com (click forums, then subwoofer tests) are
still available. Unfortunately they don't show the particular models you
identified.
Marty