SteamOS Debian Main Repos

http://bit.ly/1jKAWWV

sudo nano /etc/apt/sources.list

# Debian Main
deb http://http.debian.net/debian wheezy main
deb-src http://http.debian.net/debian wheezy main
# Debian Update
deb http://http.debian.net/debian wheezy-updates main
deb-src http://http.debian.net/debian wheezy-updates main
# Debian Security
deb http://security.debian.org/ wheezy/updates main
deb-src http://security.debian.org/ wheezy/updates main
# Debian Multimedia Repo (for XBMC 12.*)
deb http://www.deb-multimedia.org wheezy main non-free

sudo nano /etc/apt/preferences

Package: * Pin: release a=alchemist Pin-Priority: 900
Package: * Pin: release a=wheezy Pin-Priority:-10

gpg --keyserver http://pgp.mit.edu/ --recv-keys 1F41B907
gpg -a --export 1F41B907 | sudo apt-key add -

apt-get install deb-multimedia-keyring

sudo apt-get update