PA Speakers for Parties

I am brand new to this whole scene. I am in a fraternity and got elected to run certain aspects of our parties. What we need are PA speakers (our old ones broke) They need to be self powered, I am not really sure what exactly a decent setup would be but parties are generally in a huge room with close to 100+ people. We had two older speakers that managed for a few years before biting the bullet. Anyone have any leads they can give me or tips, brand new to this whole thing.
Check out the Behringer Eurolive series. You might have to raise your budget to the $400-500 area.
JBL Eon series. Built like a brick sh**house, and sound pretty damn good to boot. They are nearly indestructible, unless you do something really foolish.

That said, be nice to your neighbors and don't torture them with throbbing bass until 2am. Remember, someday you'll be living somewhere, working an actual job and needing to sleep. Karma can be very cruel.
With average tuition coming in at $25k/yr. you need to get more funding. Assess each member $500. Get something sweet that will put you guys over the top when it comes to the hottest raves in town.

I don't think this is the right place to look. This is more home audio from simple to extreme but people are looking more for more high quality from a listening spot than filling a huge room with ass grabbing vibes.
I agree that $300 will just not no no...but a grand might get you close. I am a veteran live sound pro...I sue me! Now that that's out of the way I can easily suggest a pair of used Mackie SRM450s and any cheap used mixer (Behringer maybe). Pair 'em with an inexpensive used big powered (15" to 18") sub from, again, anybody, and it will take the heavy bass lifting off of the main speakers and allow your dubstep binge drinking party to get the cops called every time! Use the failed careers of musician wannabes as your key to this thing...bands sell good stuff cheap all the time.