at 1280x1024 you will never know the difference in most cases. why did you sell the gtx460 in the first place?
and honestly its time to get a big boy monitor. you have a decent system yet you game at a very low res and the worst possible aspect ratio. with a 5:4 aspect ratio monitor you are literally missing out on 1/3 of the fov in modern games since they are designed for widescreen.
I agree with the others. At a resolution of 1280x1024, you won't notice a performance change on most games, your video card is perfectly capable at that resolution.
Edit: I saw that you sold your video card... I suggest you choose a new monitor and then buy a video card capable at gaming at the native resolution.