It's definitely possible, I actually used a 9500 case for this exact purpose.

In mine, I had a FireWire bridge board, a DVD drive and hard disk mounted in the case as normal, and a 6100 PSU at the bottom. Connected it all up, and then plugging the '9500' into a Mac via firewire you would have a nice external drive setup.

If you have the mobo and PSU then you could do a much cleaner version than mine by using the SCSI port. A bit of soldering and it should work nicely.