The Seagate Barracuda IVs were quiet. The Vs were not. Having not heard 5 in one machine, I can't speak to whether 5 Barracuda IVs would still be quiet. And there's also the cooling to consider on a drive array.

I've not read much about the Barracuda 8s, perhaps Seagate has finally gotten back to the quiet. However, even quiet drives can build up in noise when you have more than 1.

I am the Doctor, and THIS... is my SPOON!