My opinion:
Top tier: LG and Dell
Middle: Samsung and Asus
Bottom: Other (Acer, BenQ, etc)
Be sure to watch the warranty and return policy. That's the big difference between Dell and some of the bargain brands. Exact model should be dictated by you price constraints, size needs, and usage needs (feel free to provide).
If you do not already know the difference -- google TN vs IPS vs PLS and read about the kinds of panels.