honestly 500 wont get you very far as far as 'studio quality'
that term, 'studio quality', means different things to different people.
folks that own serious studios, will drop four thousand dollars on a set of monitors without blinking.
pros, 10 grand easy.
but if that's the budget, that's it.
do a lot of research.
i like the KRK line myself, yamaha makes good monitors, Jbl, maudio, Mackie.
if you can up it to about $750, you will have several really decent choices in that range..
but it almost does not matter WHAT you get, if you do not treat your room first.