I talked to a local car audio guy who has done these and he says the stock sound system is really suck. You have to put a subwoofer in somewhere and waste cargo space. I talked to bavsound and they don't make any e53 kits anymore sadly. I ran into a couple threads on here with a small subwoofer box in the cargo area. I don't love that idea. I haven't got back to researching it.

Hopefully someone has a proper sound system and can chime in.

The prior owner did a half decent job on an Android head unit but it still sounds like complete ass. Early 2000 BMW you would think had good sound systems, but no, terrible quality sound. My E36 is even worse, complete joke. Its so bad I thought it wasn't wired correctly, but it is.

I'm an idiot and I had the headliner down and I didn't put a tube up there to run some wires. That would have been really smart.

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'05 E53 3.0 6mt
'17 F30 340ix 6mt
'96 E36 328is, in progress