If you are looking for a good 23″ monitor, my recommendation would be the Dell S2340M 293M3-IPS-LED Monitor, priced at around $150. I own this monitor, and the images are very crisp on it. It uses IPS (In-Plane-Switching) in the LED, which means the monitor has bolder contrasts and is viewable at wider angles.
This monitor does has limited inputs (DVI-D & VGA) compared to the Dell UltraSharp U2312HM which adds a DisplayPort. Also, it doesn’t come with a DVI-D cable — only a VGA cable. So those without a DVD-D cable you’ll have to get it separately for about $3.