Good ideas here, all.
I vehemently avoid the appliance route. I can, with parts on hand, replace/repair a system at a site (we have 24) in never more than 1 day, usually several hours. We have a PC on the shelf to shove out when needed.
I was called by a former employee last year to look at an NVR appliance at her location (new job) because they couldn't connect to it. The ethernet port was borked. The device had a mainboard with everything soldered to it. No slots, nada, zip, nothing. The company that installed it said that they would gladly replace it for them for $2200 since they couldn't repair the one in service.
I use GeoVision (it was here when we began to install these) and they work fine. I have analog HikVision cameras mixed in feeding an 8 port video server made by GeoVision that connect via ethernet to the NVR without additional off brand licenses.
There are so many brands that recommending anything that you don't have experience with is hard. I'm sure that there are many here that would disagree, but poke and hope. There are many good brands and systems out there. I've used Pelco, Axis, HikVision and GeoVision. All are good, some are quite expensive.