I have the empeg installed just as you do in my M3, i got all the wires, plus tuner in there. Yes I have to turn it up above 0 db when I have the windows down. It's because the factory stereo does a little amplification before it goes to the amp/crossover unit. I'm content with this set up though, because a) I can hardly (but i can) notice a difference in audio quality at + 10 db. b) when I turn it up past 0 db I generally just want it loud, cause with wind distortion, i can't hear if its perfectly audibly correct. If you want specific details about the E36 standard audio setup ask me, it's complex.
- John
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1998 BMW ///M3
30 GB Mk2a, Tuner,
and 10 GB backup