Have you considered using a couple of USB drives?
If you get two, (probably $100-150/drive USD) then you have have one plugged into the SME server and the other offsite. Rotate them once a week.
I hate tapes. Did I ever mention that. There are some pretty scary statistics about how often tape drives fail even experienced administrators. HDs seem so much easier to use and more reliable.
However, I'd be curious to hear what this thread comes up with. Oh... and I'd probably look at a TRAVAN ATAPI drive:
http://www.cdw.com/shop/products/default.aspx?EDC=660722Be sure you include the price of the the tapes.