I found the answer while I am searching my-self but answer is here.
The magic's name is: "BusId".
Fixes the problem.
death@triQuad:~> cat /etc/X11/xorg.conf.d/50-device.conf
Identifier "ATI 3300 IGP"
## Required magic for radeon/radeonhd drivers; output name
## (here: "DVI-0") can be figured out via 'xrandr -q'
#Option "monitor-DVI-0" "Default Monitor"
System works almost perfect. One little glitch is I think I couldn't put my bart sleep/powersave mode in linux yet. Currently takes ~25W alone.
Thank you for the hint