@ etarasoff, Im running a pair of Aura shakers underneath my seats. Im powering them with a very small amp with a remote level control knob. I can control how much rumbling I want at the reach of my fingertip. Hard to explain but basically they are cone-less speakers. The voice coil moves up and down like a regular speaker but instead or creating sound, they create movement aka "shaking" They are attached to my floorboard (had to cut the carpet out, you can't notice since underneath the seat). Besides a good rumbling on your bottom, the floorboard is being used as the cone of the speaker transferring the shaking into an audible signal.
The point is that it tricks your brain into "feeling" the low frequencies. Some people have jumped in my car and they keep on looking for the subwoofer. It feels like an eight or a ten inch woofer. Im totally pleased with the results and Im not looking for the never ending quest to add a subwoofer anymore. Don't get me wrong, you wont feel the sound pressure level of a subwoofer but you will feel the rumbling. I recently changed my car battery for a new one and I have to say this things rock! girls love it! If anything, I would have used a single one per seat. Easier to install and less carpet to cut. I did apply black duck tape on the floorboard to prevent unwanted metal to metal shaking noise. did I say girls love it?
