Buy High Pass Filter or KAB RF1?

@craigert I am having the exact same problem and dilemma about what to buy as you are! Wow...was about to post myself. I ordered some Harrison Labs "FMODs" (20 Hz high pass)..I plan to put one on one channel to start and see if I can hear a difference in sound. I hope they solve my woofer pumping.

My Focal Aria 906's are getting "woofer pumping" when I use my turntable as well.  I've tried EVERYTHING, it's not an isolation problem (verified by moving it all over and trying different experiments...and making a digitial recording from my 'pre-out' into a digital recorder and playing it back, the problem STILL persists!)
@stereo5 any idea what's actually causing the problem? I have the same issue as you can see above in this message :/

@craigert I'm sure it will...I had someone come over today with a preamp that has a subsonic filter built in and the issue went away. I can't speak for the KAB, but I may have to buy one someday as well so I hope you let us know how it works out if you do buy one :)

@craigert No problem!  In my case I don't think it's a feedback problem, as I recorded (without the speakers on at all) to a digital recorder and played it back and the woofers still pumped. 

I feel you on the passive filter...but for $25 I think it's worth a shot. I ordered them on Friday so got 15% off, which offset the exchange rate a bit.  Still cost me $20 in shipping though. Insanity.