Powered loudspeakers? WHAT'S BETTER?

I need pa loudspeakers that have a 1/4 line input. They must have a built-in amplifier. However, i'm not sure what to buy. I want to spend no more than $500 on a pair of speakers. My music has a lot of low end so I need a 12 inch or 15 inch woofer cone. I need good sound quality rather than loudness because I'm using it in my very small bedroom.