i found one of those setups on an '84 trans am,i think
that was only avalible on firebirds-rear speaker setup
had a 2-way 4x6 speaker with a long throw woofer of
about 4 1/2" in a tuned,ported enclosure in the sails
instead of the normal 6x9s.A seperate small amp of
around (i'd say)15-20w powered the woofers,i thought
i heard somewhere those woofers are of a special low
impedance(ohms)of 1/2-1 ohm much like bose speakers
I've never heard one of these systems,but i,d say those
speakers are too small to really rock,so i'd use 6x9s