Honestly, I would not mess with a 27" 1920x1080 monitor. If I were going to step up to a 27" it would be 2560x1440 resolution. With that budget, I would get a 23-24" monitor with a GOOD panel(NOT TN PANEL). There are several monitors that are 23-24", 1080p resolution, and have a good quality panel. Good quality panels are IPS, PLS, VA....TN panels are cheap and not worth buying anymore with how many good panels are out there now. The Dell Ultrasharp line of monitors are really nice, as well as Samsung, and Asus. I mention those brands because I know for a fact they are really starting to put those quality panels in quite a few of their monitors now........not because they are the only people who make good monitors.
If you are interested in staying with a 23-24" with a GOOD panel, let me know and I can show you some.