If you're using Gig-E, then NAS should be fine. I have recently used the D-Link setup with the D-ViewCam software for a restaurant/bar/dining hall. I just built them a server with 2TB of RAID5 storage, so there was no external storage to worry about at all. I don't know about having this managed by a third party, but it's really easy to get working as long as you can get the motion sensing set up. Then it only records when something is in the view of the camera, saving a bunch of recording space. You could easily, and pretty cheaply do 3TB of RAID5 storage, and it sounds like you would only need the 4TB if you do 32 cameras down the road, in which case, you would have time to save up for SAS. I built the server with just a core 2 duo for less than $2000.
