(Debian based) SteamOS, HDMI and Xorg

Hi, I installed Debian based SteamOS on a Intel NUK i5 Box with HDMI connecting a Samsung UA32C4000 TV. The graphical installer works but after installation the start of X11 fails (just stripes so it does not get the resolution right) well, some xorg.conf and xrandr magic seems to be required. I will come to that. However, the graphical installer works.. Could I "steal" the information from it to get the right monitor data? Any ideas welcome Peter