What would be a good amp/sub/box to get?

I already have 4 pioneer speakers, but what headunit/amp/sub/box would be good for my civic? (2002 sedan ex). I know peopel at bestbuy that can get me they're discount, so i can afford to get some fancy stuff. I dont' need a system that will knock me out of the car, but something decent. Like how many watts should my woofers be, shit like that.

oh yeah, and i HATE it when my trunk rattles.. will it rattle with my new car? and how can i prevent it