I can only give my experience on what I've got, but anyway, I've got a pair of KRK Rokit 5s, and they're pretty great. I'm also using a subwoofer to fill out the low end a bit, because with 5" drivers you don't really get there.
The only annoyance is that if you're playing music too quietly, you get under the power saving threshold, and they just switch themselves off.
As for your mix, you might want to look into the acoustics of your room as well; if you've got speakers stuck in a corner, that might amplify certain frequencies and swallow others, affect how you perceive your mix. It's usually a good idea to listen to your track on multiple sound systems (studio monitors, shitty earphones, phone speakers, car radio) to try and come up with a mix that works everywhere.