Sub $700 dollar PC capable of running this game.

[plutomaniac]

GPU: http://www.newegg.com/Product/Product.as...6814131374
CPU: http://www.newegg.com/Product/Product.as...6819103727
Mobo: http://www.newegg.com/Product/Product.as...6813128510
RAM: http://www.newegg.com/Product/Product.as...6820231444
PSU: http://www.newegg.com/Product/Product.as...6817139012
Case: http://www.newegg.com/Product/Product.as...6811119196

This system should be able to more than capable of playing Amnesia. Total price: ~$688.

The system that you suggested is excellent but for playing OpenGL games always prefer Nvidia graphics cards. So, I only changed the gpu(at the same prise of course):

GPU: http://www.newegg.com/Product/Product.as...6814133326
CPU: http://www.newegg.com/Product/Product.as...6819103727
Mobo: http://www.newegg.com/Product/Product.as...6813128510
RAM: http://www.newegg.com/Product/Product.as...6820231444
PSU: http://www.newegg.com/Product/Product.as...6817139012
Case: http://www.newegg.com/Product/Product.as...6811119196

Prise: $684,94