$200 isn't a lot to work with for stereo. To get a decent amount that sounds decent as well I would estimate you would need more like $400. Remeber that you'll need:
A subwoofer
An amplifier
A box
The wiring
And if you don't plan on doing it yourself--The installation time.
I would say your best bet since you don't want to get it off the internet is to go to Best Buy. They tend to be a little more expensive than internet places, but they do offer package deals. I've seen Sub/Amp/Box combos for under $300. Get one of their fliers and check it out, or go to the store and see what combos or offers the have. Good luck.