Another option would be to upgrade the 8.6 machine to 10d and install the CASO (Centralized Administration Server Option)
This will allow you to do quite a few things such as:
Centralized management for both media servers (ie. selection lists, policies, jobs can be created from a single instance of Remote Administration Console)
Centralized Catalogs (All catalogs are stored on the Central Admin Server regardless of which media server the job runs on)
And here is the best part... You can have jobs utilize the tape drives on both servers... so if you take your
backup job of the current "8.6 server" and cut it up into a two pieces you can run both parts of the job at the same time to different tape drives on different servers.
Just an idea I though I would kick around as I do it here for ease of management primarily but also for the aforementioned reason in a few cases.
CASO Information can be found in the Administrator's Guide
Jean