I'll add that my Dahua NVR has been extremely reliable over several years. UI-wise it's kind of a mixed bag: Not the most user friendly or intuitive thing around, but once you learn its nuances it's fairly easy to get your job done. Certainly not anywhere close to being the least user friendly software out there. I use the smartPss utility to do almost all of my viewing, and log directly onto the cameras to configure them, so I don't use the NVR's direct connect or web interface very often. It just goes on reliably recording day after day. You also will be faced with the decision of getting an NVR with a built-in POE switch or using an external switch. I prefer external which gives a lot more flexibility at the expense of having to learn a bit more about networking. You'll probably get responses promoting
Blue Iris instead of an NVR. I once considered switching and decided to stick with the NVR. Had I started with BI and considered switching to the NVR it wouldn't surprise me if I'd be saying the opposite thing. I have to say with all of the information out there it's hard to get it right the first time. I started small, and after what I learned over six months or so I dumped what I got originally and started over.