Can one test e rx on a sandbox?
You can test the eRx on version 6, if you have eRx working already on an earlier version. Backup your database to an .enc file. Do a new "full" install of version 6 on a test computer or virtual machine, and then use Restore from the backup you made to create a version 6 of your database on the test machine. Run the version 6 database tuner. Log onto AC on your test machine -- eRx will work, both the new Rx and the refill requests.
I've done this on a test machine and I can see how eRx runs on both version 5 & version 6, and I think version 6 eRx is noticeably slower.