I have a 2000 E320. Here's what I want to do; add an amplifier to the exsisting stock stereo, disconnect the rear dash Bose speakers and add two 10 inch JL Audio speakers in a sub box in the trunk is it possible to add an after-market amp to the stock stereo? I know there are no RCA outputs from the stock stereo, but I was planning to get the wires from the Bose rear speakers and hook it up to the High Input of the Amp. Will this work? Or do I have to purchase an after-market stereo?