Comparing Thecus and Intel NAS devices.

I need to setup at least a RAID 1 Solution with 1TB capacity to protect a server and a few mission critical desktop computers (Server is SBS 2000 and desktops are win xp pro). At a later stage the the SBS server will be replaced with Windows 2008 Server and would be good if I can still use the NAS device on it. I intend on copying server and desktop images and e-mail/archived data to the NAS and backup to external USB drives for offsite backup. The budget is low so I am looking for entry level NAS solution with AD support. I have come across Thecus and Intel brands which I think will do the trick.
The Intel likely to be within budget is a SS4200-E and the Thecus would probably be a N3200 PRO or maybe even a N4100 PRO. Can you please provide a comparison and make a suggestion as to which unit would provide the best performance and value for money? I am open to suggestions of other brands with similar features and price bracket.