Your resolution is the approximate equivalent of a 1280x960 4:3 resolution so base performance on that, if you wish to get a WS equivalent to 1024x768 you could try setting up a custom resolution in a game and set up 1121x701 (weird but trust me, it's a 16:10 resolution and almost an exact match to the pixel density of 1024x768).
If you wish to have the best balance between image quality and performance you could try using 1280x800 and use 1:1 scaling (also called "no scaling") through your NV drivers, you'll get a non-distorted image and you won't have such a small image.