2000 A6 2.8L Quattro (Sedan)

I pulled out the factory subwoofer box to see what was causing all the speaker popping after a rain event. Turns out the box was filled with 3" of water. The little circuit amp was screwed to the bottom and under water. It's corroded and not working.

Buying a NEW replacement from Audi is $400. Buying a used one from Ebay is difficult as the exact one is probably corroded as well.

I'd like to buy any C5 non-Bose subwoofer box with amplifier and fit it into my factory subwoofer box for proper fit but I don't want to waste $150 on something that connects the same but doesn't actually work.

Has anyone used a different model's tiny circuit board amplifier as a replacement? Some other year models have the same 14 pin molex connector but I've already tried one but it was used and I'm not sure if it was broken or not compatible.

Has anyone done this?