I suggest you getting skygfx which replaces the graphics with the PS2 GTA SA graphics, which look quite nice. As Crepz already said, it really depends on what mods you’re currently using, what’s your computer specs and what kind of mods you are willing to install. If you want me to link you skygfx and a few other good graphic mods, throw
me a forum PM.
Edit: Don’t bother with ENB’s if you’re playing on a old system, they will lag the hell out of your game, maybe even break it, depending on how you install it.