I went through this a while ago, I ended up with the Dynaudios, they cost about $800 and they sound fantastic, at least on par with the mackies, maybe even better,
Remember when mixing on great monitors, sometimes all the little stuff you work on gets lost on most people's bad audio systems, be it car, home, or ipod.
Remember when mixing on inexpensive monitors,
you can't hear all the little things that make a good recording great. but if you can get it to sound great on cheap monitors, think how good it will sound everywhere else