[hardk0re]

You may want to look at Windows Home Server, it will give complete backup of all pc's every night. As for removing each night you can add in a few usb drives and cycle through them for offsite storage.

WHS will keep the costs low for licensing, etc and be fairly easy implementation (10 computers or less).

If you want central backups, email, etc all in one server Small Business Server is another good option. Alltho not as easy to implement as WHS.