I don't know the best one, but newegg and tiger direct have some nice monitors for around that.
Make sure to compare the dpi, contrast ratio, display color etc listed in the specs. I believe the resolution and contrast ratio are the most important things. I dont even think they have dpi come to think of it, thats mice. Do some comparison shopping on those 2 sites and it will be pretty hard to end up with a bad monitor for the money.