Setting up a BackUp system

im in charge to setting up a backup system for my Dads Architectural Office, he got a Hybrid Network with one Snow iMac SE, two G3 beige towers 266 ( i hope well change these this year!) running OS9 but im waiting to Jaguar , also ports for 2 TiBooks and in the other side there are 3 PC's running Windows 2000 and XP all over a Ethernet 10/100 network . so this is the question:which do u i think is the best hardware Backup solution for a network like that (we produce great amount of graphical material:cadd drawings, photos, walktru's, also grapghic design and 3D modeling from time to time) and is there a Hybrid software solution for both Mac and PC's that made a weekly backup of whtever is important and put it in one place?

thx for your help

 

let me take a look at it thx!
and what about the backup media what do u suggest?