I too have had great success with Adaptec SCSI cards.  Currently using a
PCI 2940UW with a DDS-2 tape drive and Plextor CD burner.  If you have
lots of disk space and are on an internal (secured) network, backups to 
disk over NFS work good.  Use dump each night from cron.  Put the data to 
tape as often as you deem necessary (nightly, weekly, monthly, etc...)
Personally I do backups nightly to disk, weekly to tape and about every
3-4 months a burn a cd of my most critical systems.  For the NT box, use
samba.

In case you missed my backup presentation:
http://thinkunix.net/docs/backup-overview/

Raymond Norton wrote:
> I need to implement a reliable backup system using tape.