Should I upgrade my 19" 1440 x 900 monitor to a 21.5" or 23" 1080p? I feel like I might be missing a lot of detail in most newer games, but at the same time I don't want to turn down a bunch of graphical settings. I would also like to get the most out of my recent hardware upgrade, which at 144x900 my hardware might be a bit overkill.
I run 2x GTX 460 SE's (slightly lower than standard 460s). I run 2x 1080p screens without any issues whatsoever. I am getting 60 FPS on max settings with Tomb Raider. I've noticed that changing peripherals is the most noticeable when comparing PC upgrades.
I'd say the higher resolution would be an overall improvement to visual quality, even if you have to turn a few settings down from ultra to high in a couple of games to keep your framerates smooth. The higher resolution would also mean you don't have to push your AntiAliasing as high to eliminate the jagged edges.
You are correct you should defiantly upgrade your monitor.
Even without additional graphical settings the upgrade from 1440 x 900 to 1920 x 1080 will make a real difference to your gaming experience.
Personally I would recommend a 21.5 screen as this requires the actual pixels to be smaller and gives you a default sharper picture. Its not always about maxing games out.