Right now all I have is a clarion mp3 deck, CDT EF-61CFi/20 components, and an amp for the speakers. Now I am deciding on which sub(s) to get and the amount of subs to purchase. I am unasure if I want one or two subs. Why do people buy two subs instead of just one or one subs instead of 2+? My goal is a 10" SQ sub. So for SQ would one or two subs be best? Are two subs only to obtain the loudness in dbs? Thanks in advance, Mark.