You double posted. Considering it's in the same forum, it could very well be the result of a server hiccup. Whatever the reason, it's something to be aware of, as it's a major no-no in these (as well as other) forums.
I'm guessing from the fact that you need a box for this that an Alpine Type X is a subwoofer? When you request information or assistance, it's best to provide as many detals as possible. Not everyone is going to know what you product is.
These forums are about vehicle PCs and how to get them to do what you want. While there are a fair number of members who are also very knowledgable about car audio, there are far better resources on the web than mp3car.com.