This is the best graphics configuration Quality/Performance for medium end PCs.

It is a configuration created by me, I have put everything to a minimum and I've been going up little to little the what more us interests from graphics:

DirectX Versión: 10 (MORE FPS)
Textures: Very High
Shader: High
Shadows: Normal
Reflections: High
Water: High
Particles: Normal
Grass: Normal
Post FX: Normal
Anisotropic Filtering: x16
Ambient Occlusion: High

Installation:
1. Download and extract it.

2. Open your current Settings.xml.

3. Look for the line where it says your graphics card model, and copy your model, (example: VideoCardDescription NVIDIA GeForce GTX 660 /VideoCardDescription "Copy only the model". Example: NVIDIA GeForce GTX 660. And paste it replaces only the model in the Settings.xml discharged.

4. Once changed its model of graphics card in the Settings.xml discharged, only remains place your resolution, (If you 're going to play a 1080p , it is not necessary), in the line: ScreenWidth value="X" / and ScreenHeight value="X" / (Example: ScreenWidth value 1920 and ScreenHeight value 1080, or ScreenWidth value 1280 and ScreenHeight value 720, or ScreenWidth value 1440 and ScreenHeight value 900, etc...).

5. Save and put in "Documents/Rockstar Games/GTA V".