My feeling is that the KAB is a state of the art device having used it. I am not technically very knowledgeable but the KAB website would lead me to believe that the rumble it is attacking at 140 hz. is strictly related to vertical modulation caused by warps, whereas other subsonic crap which is actually recorded right onto the record is eliminated at much lower levels. Kevin at KAB would be able to shed more light on this if you contacted him. I can only tell you that my experience is that the KAB essentially did the same job in my system (in terms of eliminating woofer pumping due to subsonic issues) as my new (and much more expensive) phono preamp with a very sophisticated subsonic filter (-9db @ 10 hz, -18db @5 hz and -48db @ 2 hz) does.
And don't confuse what's in the Bellari or some of the cheaper phono stages with a top notch high quality subsonic/rumble filter like the KAB if your system really deserves it. I recently had David Hadaway (at DB Systems) install a very basic subsonic filter in a MM phono stage of his that I purchased used for my son's system. He was going to charge me all of $10 to do it, but I told him to bill me $20 (great guy, great products, great service). It was simply a matter of soldering in a capacitor and that phono preamp is now -3db at 27 hz. which is certainly fine for that system and has eliminated all woofer pumping.
As it stands, FWIW, I have the KAB unit now sitting here doing nothing, which I would sell for a reasonable price if you are interested. It will involve buying another set of interconnects as well, but I can assure you it will solve your problem in a high quality way.
I would wager that your speakers (as mine) are ported.
