finally I played Amnesia with this settings:
resolution: 800x480 fullscreen (5:3 ~ 16:10)
texture quality: medium (impossible to solve an enigma with low quality)
shadow quality: low
shadow resolution: low
texture filter: nearest
SSAO: on
edge smooth: off
world reflection: off
anisotropy: off
SSAO resolution: medium
SSAO samples: 4
parallax: off
despite this settings it was a very scary experience! after playing amnesia I had to play an hour of super meat boy before go to bed!
congratulations frictional!
last question: is it possible to enable subtitles (english or italian) for developer commentary? are there any transcriptions of these commentary on internet?