Lots and lots of options within that budget, I would start researching heavily before buying anything. Are you trying to fill a room with sound or do you want to listen sat at a desk. How big is the room? Do you want a 2.0 or 2.1 set up? Where in the world are you as prices can vary a great deal depending on location?
I would look for a local pro audio store in your area or a national supplier, I am outside the US but I here http://www.guitarcenter.com/ and http://www.sweetwater.com/ are pretty big names. There is nothing like listening with your own ears and photo's never do justice compared to seeing things side by side.
Some brands to give serious thought are ADAM, Genelec, Focal, KRK, Dynaudio, Mackie plus a few more but these 6 would cover your budget constraints completely.
Worth considering most of these speakers are designed for critical listening in a production environment and they can sound a little flat/cold compared to more hi-fi set-ups. This is why I recommend a personal audition, I may be over-stating this issue a little because your ears do adapt to a change in set-up very quickly and you can always EQ to add more warmth if things sound too flat.