There are a few pre-configured setups like ClarkConnect that are Linux.
But you have to understand that any Linux distro has ample capabilities. When you using it your using the same software that is used in a range of hardware from Geode-based embedded platforms to servers multi-million dollar fortune 500 companies.
Remote administration is accomplished thru a veriaty of means. If your using a Linux desktop you can use X-over-SSH to get remote GUI apps running on your local computer. You can use putty.exe to get command line access to your computers (The unix shell is what all professionals use the most of.). You have Webmin that provides web-based configurations. Different services like CUPS printing has webbassed configurations by default. You have VNC and all that.
So if you want 'NAS' to mean: "Network storage computer that requires no keyboard/monitor/mouse", any Linux distro can fuffill that role in spades.
My personal recommendation is to use Debian Stable. When you select the 'file server' role in the setup I beleive it installs NFS, SAMBA (Windows network file and print services), and Appletalk by default. You'll have to install Webmin thru apt-get, but that should take all of 13 minutes to do.
The hard part is getting use to debian, linux, and apt-get. It is worth it, beleive me. You can use those skills directly to deploying all sorts of software from BSD unix boxes, to using Ubuntu as easy-to-use desktop systems, and so on and so forth. And it is one of the few Linux distros that has half-way decent documentation.
Otherwise if you don't want to put any work in check out semi-commercial setups like Clarkconnect, which may or may not be the best choice.
Check out Google and
http://distrowatch.com/ for more details.