Thank you for your help,
I ended up finding a store on ebay that is selling 9.1G drives
w/carriers for ~$100 ea. Going to just buy three more and fill up the
back plane and be done with it, I know I won't be needing to add
another backplane anytime soon, as we're only now starting to hit that
13.5Gb limit provided by the 3 4.5G, an additional 27Gb should keep us
sitting pretty for the forseable future.
Thanks again, and have a good day.