Can't you just tap into the powered outputs of the stock amp and run a line output converter? That is what I would do and what has been done. The Peripheral converter is great. I would also check out the PAC line output converter. I have used PAC in all my installs that ive done and couldnt be happier for the price. For more channels and processing i would use the Audiocontrol LC6i. That is what many other board members have used in the past. There is also the Rockford Fosgate 360's but thats only if you want alot of adjustability and processing features.
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