I would start out with 512 textures & only preload into memory, in game leave your detail settings at "default". Pull up the ctrl-I pane & see what your frame rates are. If they are above 50FPS with your clipboard up sitting in the tower, you can probably get more detail & higher texture (1024 tex. pack) settings. You may want to test it out by flying around in busy areas before bumping up the detail though. (level of zoom affects your frame rate also, keep that in mind)
