I cannot emphasize how important it is to test studio monitors out before you purchase them. Every producer has different requirements and you really need to hear the monitors in action before you purchase them. I typically buy products online, mostly through Amazon.com because of the price advantages, but with monitors I really needed to go to a store to check out the options.
My local store is GuitarCenter and they had a nice array of monitors to choose from. I listened to the KRK RP6G2 Rokits and then compared them to others. Purely from listening to different genres of songs (particlarly genres I produce most predominantly) I walked away with monitors I had NO intention of purchasing when I walked into the store. This sounds like a advert for GuitarCenter, but I loved how I got to use their listening booth all by myself and crank-up the monitors however loud I wanted them.
The monitors I chose in the same size + price range as the Rokits were the Mackie MR5s:
http://www.guitarcenter.com/Mackie-MR5-Active-Studio-Monitor-104786603-i1386321.gc
What did it for me was the clean, visible, honest bass. For me, and for the audio I mostly produce (electronica, dance, drum and bass) bass is very important to me. The Rokits had zero bass in comparison to the Mackies and I was very pleased with the performance. Mackie also make a higher performance MR8 if you have a bigger budget, but the MR5s met my needs perfectly.
So the advice I would give anyone about monitors is test them out first in a store, compare against other monitors in your price range + size range, and test them out with a genre of music similar to what you will be producing yourself.
Good luck finding the perfect monitors for your needs! 