01 audi a6, amp power wire to battery

Is the battery in the cowl?  Usually what i do on Audi's like that is, over on the driver's side of the cowl is a plastic box with some computer type components inside it.  If you pop that open by removing the 8mm (IIRC) bolts from the top, you can look right down into the cabin area by the pedals.  Now on that box, closer to the battery, is a cormer that is nice and flat and has nothing coming in or out of it.  I usually drill a hole large enough for the power wire as close to the bottom as possible.  Once I run the wire through it I seal it up with silicone on the inside and outside to keep any moisture from getting into the box.  Even if it did, the hole is close to the bottom so it would just run back out, but it shouldn't get in in the first place.

Not sure if yours is set up like this.