Dell U2311. Without a doubt. 1080p IPS panel, 23 inch for $300 or so (I haven't checked to see what it's price is right now, but it's always around 300). Pretty much anything else you'll find in this price range will be a TN panel, which is miles behind an IPS in image quality.
Oh, and moto nack, that "very good contrast ratio" is a load of marketing crap. All LCDs run at roughly 1000:1, unless they are terrible screens (such as those found in some laptops), which are well below 1000:1.