I need to provide my company with a new dedicated file server system.
I would like to use a windows server based NAS to take advantage of
VSS and the previous versions recovery capability I currenty enjoy
with my windows2k3 server shares.

To complicate things, when setting up this new NAS, I plan on
purchasing two sets of hardware/software and mirroring the data across
a WAN using DFS-R to provide an extra layer of protection for my data.

Would I be better off using Windows Storage Server 2k3, or going with
a regular windows 2k8 server (if 2k8, should I use the core
installation?)

I originally liked the idea of WSS2k3, but I can't find any
information about microsoft's future plans for that OS and don't want
to invest in it if its successor is right down the road. I"m also not
sure about IPv6 support in WSS2k3 which makes the new network stack in
2k8 more attractive to me to use as a file server.