Since you're mostly Intel based, why not a Win2K solution?  I know of a very
large site that backs up over 600 GB per night from well over 100 systems to
a Dell Quad Xeon, SAN storage, STK Powderhorn with 9840 drives (10 total).
Their database is over 100 GB.  I don't think you have to rule out the
platform that you are probably most familiar with.   Give it a try.  If you
need a contact, email me off the list and I'll provide one for you.

Thanks,

Kelly J. Lipp
Storage Solutions Specialists, Inc.
PO Box 51313
Colorado Springs, CO 80949
lipp AT storsol DOT com or kelly.lipp AT storserver DOT com
www.storsol.com or www.storserver.com
(719)531-5926
Fax: (240)539-7175