I do not personally have experience with your new storage, but Raid-6 is acceptable for backup storage.
Even NBU appliances uses Raid-6 for dedupe storage.
To migrate to new server and storage, I suggest the following:
Before intended cutover, ensure ALL images on Advanced Disk have been duplicated to tape.
Expire all disk images (important to only expire disk copies) and remove Advanced Disk config from NBU config.
Run catalog backup and recover on new server.
Re-run device config on new server to re-add robot and drives (paths would probably be different).
Add new storage to NBU as Advanced Disk or MSDP. Update policies and/or SLPs with new STU.
Documentation:
Using catalog backup and recovery to transfer NetBackup catalogs between Windows master servers as part of a hardware refresh
http://www.veritas.com/docs/000041076