never liked JL... I get too many of their blown products... and they sound like crap... a pro series boston will put anything comparable to shame... hands down. You probably listened to an older Rally series sub... they sounded good, but did lack a little punch. The Generators that replaced them, I would also put up against anything comparable.
I went to CES and saw and listened to the Boston amps... plus the Boston Isuzu Axiom was up here, and was running them. VERY, VERY nice! Ive also been to Boston, in mass... they had them available for demos when I was there... so, yeah... ive kinda heard them... plenty of times.