I've got 3 WD blacks in a bottom of the line Tuniq case sitting about 1ft from me, and the video card is really the only thing I can hear at idle. If you copy some large files around you will hear the drives, but nothing that seems overly loud to me. I will never buy WD drives again though, after they essentially disabled the ability to use them in anything other then stand alone, and Raid 0/1 sets.
I didn't notice the Sata 2/3 thing earlier, the drives I am using are Sata 2.