I use the LaCie 3TB d2 USB 3.0 Thunderbolt Series Hard Drive with my MAC Book Pro computer. See:
DataTale quad bay Thunderbolt drive http://oyendigital.com/hard-drives/store/RS-M4T.html
Filled with 4 Hitachi Deskstar 4TB drives.
Looking forward to high quality Thunderbolt cable to try between this storage unit and my Mac Mini.
Like you, I have an OWC case, but the drive was modified by Benjamin at Mojo Audio. He put in a 4TB AV drive, added some sound proofing and/or vibration absorption, and the drive is almost completely quiet. You have to be right on top of it, without the music on, in order to hear it.
As a photographer, I have many other drives, including the standard OWC Mercury Elite Pros, which is probably what you have. They're all too noisy for the stereo. I also have a couple of OWC Raid drives that sound like the local regional airport.
I use Seagate server grade drives in my NAS in a mirrored RAID config. They are quiet and very tough.
Started out using regular drives and they failed in a few months
RAID is very tough on drives, so server grade is important - according to my friends at the computer store.
Got the same RAID config drives on my photo processing machine and the are great.