I recommend to install e17 only in Sid. The reason is that the official e17 packages are in the experimental repository. There are several repos for e17 but in my personal experience I prefer the official ones.
To add them you need to add these lines to your sources.list (you can use any server)
deb http://http.us.debian.org/debian/ experimental main contrib non-free
#If you want to use the sources
deb-src http://http.us.debian.org/debian/ experimental main contrib non-free
Then edit your /etc/apt/preferences (create if needed) and add these lines
Package: *
Pin: release a=unstable
Pin-Priority: 700
Package: *
Pin: release a=experimental
Pin-Priority: 600
Then issue apt-update && apt-get upgrade and apt-get install -t experimental e17
Debian Adventure 