What’s the best Nas device?

I have a small network of 6 pc’s w/xp pro. The server is a dell poweredge 1300 running NT4. They will not change tapes for backups and I’m not always there. They have no raid on the server either. My thought is get a 1 or 2tb nas w/raid(ethernet)and just use that as a backup. Plus they could use the extra storage. Only 80gigs on the server. Any suggestions on brands and experiences w/nas would be great. My budget is from $200-400. Thanks!