Stream Audio to RPi over LAN, Multiplatform

[steinerlein]

Hello Guys and Gals,

I received my RPi and periphery today and am very happy to be able to test a little stuff already
My ultimate goal is to use the Pi as an audio-proxy on my Hifi.
I use A Windows Desktop and a Windows Laptop aswell as an android smartphone. I am a Spotify Premium-user, so all things music come out of there. It's running this atm:
http://www.woutervanwijk.nl/pimusicbox/
This solution is workin. Well.. kinda.
It has a pretty high latency, my "starred"-playlist is not showing up and there is no offline-storage of my playlists.
Thus I want to find a way to stream the sound output from my multiple devices to the RPi over the already present LAN. And for the times I have not-so-geeky visitors I need to have the Airplay-functionality available, i.e. with shairport.
I have tried understanding mpd but I don't get it.. yet

Any ideas or solutions available?

[steinerlein]

Just to give a headsup for anyone searching the forums:

I am now running the following setup: Debian Wheezy hard-float with mopidy installed. It is controllable via one of many mpd control clients. I use MPDroid on my Android smartphone and GMPC on my Windows laptop. Mopidy is actively being developed and already offers a very wide set of functionalities. I am very interested to see where this project is going
For the times I have a friend over that happens to own an apple device, I installed shairport, wich works just fine aswell.
Furthermore I invested in an external USB soundcard to get better sound. This caused a bit of trouble with ALSA and the like but I got it running eventually. There are many different tutorials out there that will provide the different parts of this project.
Prior to doing this I had no experience with Linux and ended up doing everything through SSH as I am too stingy to buy an hdmi cable. It makes the RPi nice and fast aswell as it doesn't have to run a GUI.

As of now I am very happy with the setup and will be looking into integrating a wireless electricity plug to switch off the amp when I'm already in bed