hi,I need a NAS for my office use basically to backup mu UBS accounting system and microsoft office files.I have 5 computers and going to install ip cams too.So which model would you recommend?I have no idea on NAs and I was told that Synology is the best, and i read about the review of ds 713+ and I think it is quite good..so is it comes with the hard disk or I need to buy it separately?