To give you an idea what to look for in the graphs, pick a sub build from the database and model what the specs of the build are.
http://www.hometheatershack.com/foru...-database.html
Remember that all subs model differently, and the graphs will show you what is "acceptable" for a given sub, in a given design. A lot of sub builds in the database were designed for low end extension, and the graphs will reflect that.