Not OP, but you could probably run the debian version created for the Pi, and then just install whatever packages (samba, webmin, etc) you needed on top of that.
We have 1 Pi at home running RaspBMC and it's great. The thing I like most about the Raspberry Pi is that you can swap out SD cards and reboot, and suddenly have a totally different machine, doing something totally different.
That's essentially it, nothing is stored anywhere else. You could theoretically just have a bunch of disk images sitting on your desktop and write to the the RPi SD card whatever image you wanted it to run.