2500x1600 would be fine for desktop applications, or watching some movies. As renz496 stated, you won't be playing games at that resolution with your current video card though.
Also, if you get a 27" 1920x1080 monitor, keep in mind you'll want to sit further away from it. The larger screen, with the same resolution as you have now, simply means the pixels are spread further apart. This means "less detail" up close.