I think the Samsung 214T is the best LCD for a cabinet. It is 21.3 inch, 3:4 aspect ratio, it has a Pivot function and has amazing viewing angles (vertical and horizontal) and rich black. The same screen is built into the Eizo S2100 and the Nec 2190UXP as well, but they are more expensive. Response times are good as well.

Make sure you buy a S-IPS or S-PVA panel that has a maximum of 15ms G2G and says it has viewing angles of 178/178. And these do only exist as 21.3 4:3 screen or as 23,24,27 or 30 inch widescreen. All other options are crap, and below 500$ you will not find anything good. Viewing angles of panels written as 170/160 are not even close to the angles you get when they say they are 178/178's, don't be fooled by the slight difference in numbers!