Different people care about different image quality settings. Some prefer higher resolutions trading off low or no AA (me). Others prefer higher AA at a sactifice of lower resolution (i.e. 1280x1024 4AA). Then there are those who want both. Further, some players are willing to turn off high quality shadows to medium or low settings so they can crank highest resolution textures instead, while others crank textures and shadows to medium to get 100% draw distance. Add to all of this that different people are more sensitive or less sensitive to framerates (i.e. some think it's fine to play FPSs at 40-60 average, while others want 80-120).
Because of this, I suggest you first play the games you like on that 24 inch monitor (congrats btw), and then based on the settings and whatever image quality reductions you are comfortable with you can decide if it's worth upgrading or not. For example, I can play Colin McRae at 1920x1080 with everything on High/Ultra without AA and no AF on 8800GTS 320mb. The minute I turn on 4AA and 16AF, performance drops to 1-2 fps. Am I going to make a big deal that I can't run 4AA/16AF in that game? No, because reflections and textures make it look good to me, not AA or AF. But some people might.
If you do decide to upgrade, I'd try to hold out until Nov. when GF9 and HD 2950Pro come out (but since you don't play a lot of games, maybe you can lower some image quality settings and be happy with them - only you will know).