The sticky supported drive list is hopelessly out of date. Most of the drives on it are not manufactured anymore. I am using two 1TB Hitachi HDS721010CLA332 drives in a RAID 1 configuration, which are the presently manufactured version of the 1TB HDS721010CLA330 and I got them about $70 each on sale from Newegg. The HDS721010CLA330 is on the supported list, the HDS721010CLA332 is not. I did first make the mistake of buying two WD 1TB Green Drives with the Advanced Technology Formatting, but returned them. When I looked at the HDS721010CLA332, I searched on that number along with "DNS-323" and found posts of people who had successfully used the HDS721010CLA332 in their DNS-323, so I was pretty confident when I bought them that they would be fine.
Albeit, my drives are 1T drives, but as long as you stay close to something on that list and google the drives part number along with "DNS-323", you'll probably find out whether people have used it successfully.
By the way, I do use two of the WD 2TB "green" drives in an dual xenon processor (8-core) 48GB RAM workstation I have at work, and I don't have any reason to believe they are significantly less power hungry than if I'd bought someone's drives that don't have "green" in their name.