What NAS to buy?

An anonymous reader writes: Currently, I'm running an old 4u Linux server for my private backup and storage needs. I could add new drives, but it's just way too bulky (and only IDE). For the sake of size and power efficiency I think about replacing it with a NAS solution, but cannot decide which one to get. The only requirements I have are capacity (>1.5TB) and RAID5. Samba/FTP/USB is enough. Since manufacturers always claim their system to be the best, I'd like to hear some suggestions from you Slashdot readers.