alternator line noise filter

I just purchased a 10amp noise filter... to stop the line noise produced by the alternator feeding through my stereo speakers.

3 questions.

1. Is the 10 amp enough?
There were other ones to choose from, such as 20, or 30amp.
2. How do I know which amperage is correct and if it's going to work or not?

3. How do I got about installing it? It does come with a electrical type diagram on the back of the packaging.. but I don't understand it.

I've search Google and didn't find much of anything. If someone else has had this issue, please do tell.. or if you could provide with some links?

thanks again for the help :)