It is possible, but it would be moderate work and you would have to buy crossovers. These are the four challenges to address...

1) All of the cars speakers terminate at the three DSP amp plugs.
2) The radio only feeds front channel audio to the DSP amp
3) The car has 14 speakers with no crossovers
4) The speakers are designed for an amp with much more power than the radio amp

First, you will need to run the rear channel audio lines to the DSP amp area. Then you will need to decide which of the speakers you will drive with the radio. My suggestion is just 8. Then you will need to buy or make crossovers for the speakers you choose. Finally, you will need to split the radio outputs, wire them through the crossovers and then splice the crossover outputs into the individual speaker runs.

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