I recommend using pulseaudio for this, if you don't want to setup shairport and RAOP. The pulseaudio documentation describes how you can do this. You need to setup your debian laptop to provide a pulseaudio rtp sink. There is also a nice howto available on mpd and pulseaudio.
For some first tests, you can just run these commands through pacmd on your laptop to set up an rtp sink:
load-module module-null-sink sink_name=rtp
load-module module-rtp-send source=rtp.monitor
set-default-sink rtp
On the Pi, you will need to start the rtp receiver:
load-module module-rtp-recv
You can do this also via pacmd and put it later into a configuration file.