I don’t know about the Xbox 360 speaking DAAP (iTunes sharing) – but the old one with XBMC sure did.
Still, with using WHS you can run a UPnP share off WMP (I guess thats possible), and still use firefly to serve up for the Macs etc.
Now as far as remote syncing to an iPod from a shared library is concerned, I have no clue about that.
My advice is to do a test-run then you’ll know for sure.
If you use *IX as OS however, you can also run LAMP, but have to pass on IIS. I don’t think I have to name any arguments pro Unices here 😉
You could just as easy set up a virtual WHS using Vmware, Sun’s Virtualbox (the latter I can recommend), etc.
The P4 has more than enough CPU power, even with all other servers running and the virtualization.