If I were pulling a DSP amp, I would replace the amp and speakers. Here's why...

The DSP amp has 14 individual outputs that are actively crossed over. (I am guessing you know this, because you know that you will need crossovers.) Here's the challenge: You will need a three-way crossover for the front doors, a two-way crossover for the rear doors, and a low-pass crossover for the sub. The trick is finding the correct crossover frequencies for the factory speakers. You will probably not like the sound of mixing generic crossovers with the factory speakers.

I would get a 5-channel amplifier that has a built-in active crossover for the subwoofer output. Then, I would buy two pairs of two-way full-range speakers for the front and rear doors that come with their own crossovers. That way, you will get a correctly matched sound from all the new parts. You can mount the crossovers in the trunk and utilize the existing wiring pretty much as is. Or, you can use one pair of wires that feeds to each door, and mount the crossovers inside the doors. I would probably install the crossovers in the trunk and utilize the existing wiring.

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