I'm about to get a system for the first time. I found this link really helpful
http://www.crutchfield.com/S-VVuWfzGGpCq/learn/learningcenter/car/amplifiers/shopping_guide.html
Also I don't know if you have the box too but they also describe them.
http://www.crutchfield.com/S-jiBwceG2ZMx/learn/learningcenter/car/subwoofers_enclosures.html