I keep coming accross mention of the idea of having 2 raids in a server. One to handle the OS and one to handle the data. Don't forget the most expensive bit - a decent tape drive. Ideally you want a tape big enough to back up the entire server every day.

There are other things to consider as well. Do you want a tower or a rack mount? tower will be cheaper, but I would recomend a rack mount if you intend to expand. A single tower server is one thing, having 4 on the floor is another.

Then what about AC. A single server can easily put out 1kW of heat. Add in a person and a couple PCs and that can be one warm room very quickly.

Some of this is probably beyond what you will need, but as I say - if you want to expand you will need to think about it. Oh, and don't forget to allow for software lisences.