Okay... bit confused here. Let's take these two statements:
"I am looking to set up a home NAS/media/file/backup server.
I want to be able to do other things with the system on occasion, not continuous, i.e. development, etc."
In those circumstances, I would have plumped for one of the readily-available NAS distros that's built around a familiar distro then look at extending its functionality. I'm in the process of building an XMBC machine then dropping additional server packages (apache, pure-ftpd, sshd, postfix etc) rather than build a server and shoehorn XBMC onto it.
However,