You just described the use case for the DSR1 I mentioned earlier plus an amplifier. Noting that the amp will likely need to drive all the speakers and not just the sub. Also still not sure if it works for the Outback as I haven’t seen anyone using it. Idatalink says yes. I expect this is plausible, but I’m sure they sometimes get the comparison wrong.
When I did it to my Focus I pulled the factory amp and replaced it with the DSR1. I plugged the DSR 1 output into an amplifier. The amp output was wired back into the factory harness to drive the speakers and sub. Noting that I also replaced all the speakers and sub, but kept the stock locations and under the stock box. Used a shallow sub box to avoid replacing the factory sub box. The added bonus here is that the idatalink wire harnesses connect directly to the stock locations (Again assuming it works as they say). No stock wiring hack. The most difficult part of the installation was finding space for the amplifier mount and the amplifier wiring.
When the DSR1 works, you end up with the stock look, but the aftermarket sound (due to the removal of state-of-the-art DSP, more power, and updated speakers for the locations you update).
