I currently have a FW800 Drobo, which is about 5 yrs old and has been passed onto my parents, so I'm looking to replace it with a NAS box. I have narrowed my search down to 2 models; Synology DS413j and Qnap TS-412. I like the Drobo, it has served me well and I've had no problems. It is used exclusively to house my iTunes library, and this is what the NAS will also be used for. The features I really like are the ability to mix and match drive capacities and brands, and to increase the capacity of the Drobo by simply adding a larger capacity drive. I would very much like to have these features in the replacement NAS. I have looked at the spec sheets for the Synology and Qnap, they clearly have many, many more features than the Drobo, but I have not been able to establish whether they have the features I want to maintain described above. Can anyone help me with this? Thanks.