I've got a DS413+ with 4 Western Digital RED-series disks(build for NAS:
http://www.wdc.com/en/products/products.aspx?id=810 ). It took a while to get the NTFS-rights working correctly. But now I love it, and it's the brand I recommend when people ask for NAS.
The administration is vastly better than Buffalo and most other pro/consumer models.