AQ/SQ SDC 2.5 12s or 15s, or maybe AQ/SQ "1" Hdc3 12, 15, or 18? good subs for the price, sa-12s or 15s are good. there are alot to choose from from honestly. if you go with 1 nice sub that will allow you save money on a bigger amp, and upgrading eletrical less. also 1 sub applications are easier to deal with IMO lol... hence i love a good single sub setup that sounds like multiple subs