I'd look at a VXA-320 with software.
114.02602 VXA-320 Internal Packet Tape Drive Kit, Yosemite TapeWare SW VXA 160/320 GB, 12/24 MB/s tape drive, LVD/SE SCSI, int., blk, install kit containing 1 X23 data cartridge, 1 cleaning cartridge, Yosemite TapeWare SW, CD with product documentation, installation and driver tools $1,420.00
HEAVY discount available - and these guys are reputable:
The Yosemite software MIGHT be good enough to do what you need. If not, then you could buy that Backup Exec.
Here's a motherboard with onboard SCSI that is what you need - and also has a 133 MHz PCI-X slot for your Adaptec SATA RAID card:
It appears to come with a proper SCSI cable and terminator too. It's actually a few bucks cheaper than the board you originally chose. Ram is going to be different - http://www.newegg.com/Product/Produc...82E16820145308