1. Personally I don't like ubuntu much as a file server as I have had some problems with authentication taking up to ten secs, I use fedora for everything.
http://fedoraproject.org/
It has worked very reliably and very quickly for me. (Running on a 750mhz with 512 ram)
2. I understand the budgeting I believe the pci cards can be setup for raid as they usually have a built in raid chip, I have one myself during boot up I get a brief message about Configuring the raid controller (about 2-5 secs), I have looked at it, but never changed the setting by default it just acts as a HDD controller (non-bootable).
3. Putty is the way to go, very simple and powerful tool, another one I have found is tunneler,
http://www.bitvise.com/tunnelier Tunneler gives you a number of features including a GUI for transferring files to and from the linux box.
Tunneler does the same thing as putty, with slightly different features
You will need to install one of these two apps on all the computers you want to control from, (putty is 444KB, Tunneler is 4.2 MB) Both apps have been setup for U3 Flash drives if you have one.
The other option requiring no install is telnet, which may require some setup on the server, but it has the benefit of already being on all your other machines.
4. Using putty or tunneler, you can transfer files from what every computer you are on and your server, again tunneler has a GUI for this while putty is all command line. (Tunneler is a bit faster, especially if you are browsing because you don't know where the file is,
)
For a web server or putty/Tunneler you'll have to open and forward the ports on your router. 80 for web and 22 for SSH = Secure Shell(putty/tunneler service), the advantage of SSH is that all the information is 128bit (or 256bit) encrypted and is protected by a user name password by default. A Con though is that you have to have an SSH client on the end machine. (putty.exe can just be put on a flash drive and run from there as it has no other file dependencies)
With the web page it is easy to access, but default has no username or password (but one can be added) Web would be fine for movies or music, but you would want to avoid it for things like a resume or other sensitive information.
You could also setup a FTP, that requires login, but it has the same advantages and disadvantages as web, except it's slightly faster then a web transfer.
5. I really have no idea as I don't own any consoles
6. I can think of two of things you can do:
A. Setup a samba share
http://www.samba.org/samba/docs/man/...TO-Collection/ and then setup each computer to use the server as a network drive. Then run a scheduled task on each computer every X on Folders Y and Z to be copied to the network drive.
B. Create a shared folder on all the computers and write a linux script to copy all contains of said folder, to a folder stored on the server and the script can be written to save or overwrite existing files.
There is probably some open source software out there somewhere that can help you with this, freenas is just a file server and doesn't have a system that could handle any more then it does.
Feel free to ask me for more details on any of this.
Good luck,
Vischa