After installing an empeg into my car (with the monsoon system) I can only advise one thing. Buy an amp and bypass the monsoon. I ended up having it done professionally. You can keep the original speakers but there is next to NO low end. Visit newbeetle.org, many conversations about this.
You can keep all the wirings 'uncut' so you can go back to stock afterwords, but really consider buying a sub (which I really need to do)...

The 'Micro-Audio' amp is a dead end road.....