Is the stock amp a separate unit from the DSP controls? I was thinking of doing a simpler setup with a new amp to power the stock front speakers (either just the two or center included) and adding a powered subwoofer on the rear shelf...I would imagine the stock KEF units would sound good with more clean power. Anyone attempt this, or at that point why not just switch out the fronts with separates? I get that too...just trying to simplify the install
There are two amps, the main amp with the DSP plus a booster amp for the subwoofer. The booster amp takes the output from the main amp and, uh, boosts it.
There is no way to upgrade just the amp to get more power, you'll end up boosting the signal from the main amplifier.
I am not aware of a non-invasive way to extract the original digital or line level signal from the OEM system. The A2B bus decoder, DSP chip, DAC chip, and the amplifier chip are all in the main amp unit.