Computer Forums - File Backup System

Greetings all. I have a situation and would like some opinions.

The company I work for needs a place to store large files and have them backed up. We have both Mac and Windows that would need to access the drive(s).

I was thinking of a NAS box but then I wouldn't really have a way to back it up since a NAS doesn't run software. So, I was thinking of a RAID server and just have that backed up on tape.

Was wondering what would be some good options. Price is somewhat of an issue but not terribly.

Thanks in advance!