It sounds like you are looking for powered monitors not studio monitors. The M-Audio BX series as recommended are nice solid choice. In your price range there is not much out there that are all that great. I'd stay away from KRK stuff, you see them for cheap on the second hand market, but there is a reason. Fostex makes decent low cost powered monitors that can be found in your price, and if you want to go really cheap, Edifier speakers are pretty good bang for your buck.