We are expanding our office of 5 PCs to something around 10 PCs.
I'm looking forward to buying an IBM server for a small business with 10-12 PCs.
The server would primarily be used for centralized file storage.
Currently, our office has an old P4 (~3GHz) as the server with 4-5 PCs. After expansion, we intend to buy an actual server to serve the 10 PCs.
The NAS would be ideal if you are only doing file storage. If you wanted something different, I would look at Dell servers since they will be cheaper than an IBM server and the quality is nearly the same.