Its not worth it. You won't notice much regardless of what you do if you keep the stock speakres. Plus, I'm pretty sure all e46s have dead heads. Instead of replacing the HU, replace the amp with something aftermarket. That will yeild the greatest increase in SQ.
<span style='color:gray'><span style='font-family:Courier'>1995 e36 3 Series RIP
1999 e46 3 Series BURN IN HELL
2000 MR-S Roadster= Current</span></span>