If you can afford a 2005+ Mustang, I'd imagine you could afford slightly better equipment. But otherwise, call Crutchfield and find out how much airspace is in the enclosure. From that, buy the unloaded version (without the subwoofer) and find a 12" subwoofer that will fit in that enclosure. Or post here and someone can help you out.
Otherwise, go to a local car audio shop and have them price out a custom fibreglass enclosure and subwoofer. It might cost a bit more, but it will be well worth it.
Don't buy the one you suggested. You will regret it.
it is not good at all. Not even if you only wanted a "little" bass. Antonio, i know you are new and all, but please do not word stuff that way. I mgith just think that it is a good sub for giving a little bass when actuallity it isnt even worth the cost for the little bit that it might put out.