There is infact another product called \"q-max invisibass\".
They are basically a 6.5\" sub in a very small, flat enclosure that is designed to slot straight underneath most car seats. I cant remember the exact price, but I think they are around $200 or so.
I've not heard one in a car myself, but from reputation they sound surprisingly good for the size - they have been used in some national and state sound quality events with some success.
