Unfortunately $200 isn't a lot to work with. Do you have something to power them or is the budget for amp and speakers/sub? Anyhow here are some thoughts on where you might take things...
Some entry level subs from good brands, as you can see they break the budget.
HSU STF-1 is on sale for $254, add an extra $35 for shipping
http://www.hsuresearch.com/products/stf-1.html
Outlaw audio M8 is $249 shipped, $225 for bstock.
http://www.outlawaudio.com/products/m8.html
Your best bet on that budget is probably DIY and/or used.
Maybe the tritrix kit from parts express $239 shipped but I've seen it onsale for $199 -
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-702
Maybe some overnight sensations and a modest sonosub?
Another thought, for a taste of good sound on a budget, headphones can't be beat. A pair of Grado SR60s will give you a taste of high end sound for ~ $80. They sure won't shake your room though!