I just bought a 2001 BMW x5 3.0i. It appears to be standard, pretty much everything. No nav, no dsp, no changer. I found the amp, but not the subwoofer. My question to the experts here are: assuming it had a sub, where would it be located? Two, has anyone hooked a aftermarket sub to the current amp? I'm not looking for a big boom, but something to even out the sound.

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