I'm tryin to help my buddy find some new subs. They are going in an f-150 supercab. He bought a dual sealed downfireing box for under his seat. Each chamber is .6 cuft, and the mounting depth is 5.25in. The music he listens to is primarily rap/hiphop and rock. What are some sub recomendations that can work for him? I wana say about $800-$1000 for subs and amp/s total. Of course if it can be done for less, thats always better! Thanks much