Anyone heard of or had any experience with one of these before? they sound like they'd be sweet! I have found some on ebay for a total of $27 including postage and handling.
I found this page detailing em.
NTPOG 5th Gen Bass Shaker Installation
The ones on ebay, dont sound as beefy as the ones on that page (18W RMS), but im sure they would do something if you stuck em under your seat ;P