premium system
If you have 6 speakers instead of the typical 4... or, if you look underneat the front passenger seat, you will see a unit measuring 6" to 8" x 6" with an aluminum casing. Chances are, it will say panasonic on it. IF you find this unit, then you have a preminum system.
If you have premium system - you have a choice here. You could either choose to use it - by sending the pre-amp out from your head unit to this amp and then feeding the speakers.... Or, you can connect the wires from the speakers directly to the head unit. If you do the latter, I don't know how you can feed the 6 speakers.
Hope this helps.