If you need to reuse your DLTs then Breece Hill makes a good little library.
I am using 2 Q47s with 3 DLT4000 drives and am deploying 4 more q 47s with
DLT8000 drives.  Each holds 60 tapes in a rotating carasel.  ADSM supports
it with the SCSI library drivers.  They have been very reliable and their
support is good.  Even the call is free.  Onsite service is expensive but
who isn't and they hardly break anyway.  I know the 2 that are currently
deployed have been in place for almost 5 years.  I believe Breece Hills can
still be ordered with the older DLT hardware.

Jack