I had an amplifier board chip in an old all-in-one 2.1 PC speaker system with a subwoofer. I hooked up a subwoofer and speakers to it and it turned out to be more powerful than the amp that came with the original speakers which was advertised at 75 watts. Obviously this was a lie but these things are plain and clear at 15Wx2 and 20Wx1 for the subwoofer. I have a feeling you could use an 8 or 10 inch car subwoofer and 2-3 way 6x9 or something and you'd be fine. One caveat is that I've noticed that the low pass filter is either absent or severely absent. This little sub puts out a lot of mid to high range sound. I reduced it a bit with the subwoofer and decided to order a low-pass filter from Amazon, after all you can tune the subwoofer.
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