AT or ATX will work fine, however I would strongly urge you to use a proper CCTV power supply. I have used at least a dozen of these. 18 outputs, each channel is capable of 2A max, 10A total ...

IndigoVision Doubles Resilient NVR Storage with 2TB Disks IndigoVision ... They support fully redundant power supplies and fully redundant Gigabit Ethernet connections as well as options for RAID 0, ...