In Reply to: Head unit and amps screwy? posted by Brad Hopper on March 02, 1999 at 09:51:48:
a/d/s/ has three different upgrade options for the E36, 2 out of the 3 actually replace the factory amp with an a/d/s/ amp and use the car's input wires to the factory amp as the input to the a/d/s/ amp. Granted this is for the E36, but I think the setup should be similar since the E36 head unit has high level outputs too. Check out the following two a/d/s/ options and call them, they may be able to tell you whether you can use the same setup for the E46.
single amp upgrade: http://www.adst.com/e36/system2.html
dual amp upgrade: