Please read the sticky at the top "Sound System Improvement, Stage One". I have given a good better best break down. And although some of the equipment has been updated (Alpine sps-400 are now sps-410) the idea is the same.
Short answer is no it is not a one for one replacement where you can swap out the H/U with an aftermarket and get audio right away.
Be prepared to spend $600-800 to replace H/U and speakers along with installer fees (depending on what they charge in your area).
Replacing the speakers are a breeze with some patience and minor tools. That is covered in the sticky.
I would start there.
I was going to do some trouble shooting pics for an earlier question, but I am a victim of the widespread power outage on the NE coast and it will have to wait.
2013 S4 Loaded (and NO RFT's) Awesome is an understatement
2008 MT X3
RIP you were a faithful sidekick and will be missed.
2007 AT X3 RIPOS
2000 Jeep Cherokee
1997 Twin Turbo RX-7
1984 GTI Wolfsburg Edition Neuspeed and more
Last edited by Evlengr; 07-02-2012 at 04:15 AM.