Aura Bass Shaker Pro vs Clark Synthesis 209

I currently have 2 Aura Pro's under my couch. They are cool but it seems they don't go quite low enough. During a really deep bass scene they will shake for a while then they stop and my subwoofer is still digging deeper. I was wondering if anyone had experience with both of these products and could compare them. I was thinking about returning the 2 Auras and getting 1 Clark Synthesis 209 since supposedly it is 10x more powerful than an Aura and it goes down to 15Hz instead of 20Hz for the Aura. Would it be worth the change?

Okay, how about the Buttkicker Advance? I really don't want to pay $500-600 for the LFE kit and I already have a 120 watt amp. Would the Buttkicker Advance be a nice step up from the Bass Shakers? Or not worth the upgrade? Does anyone still use these things? Am I talking to myself?