My limited experience agrees that an NVR with built-in POE is very loud, a major portion of it being the power supply fan. My no-poe NVR uses a fanless external power brick. Its case cooling fan is pretty reasonable, but not silent. Some newer PCs are about the same, some are quieter. Built in POE capability gives you plug-and-play operation at the cost of flexibility. With the built-in POE switch NVR it's a pain to log onto the camera directly. With an IT background I'd assume you could handle the network issues involved with an external POE switch. Based on my own (again, limited) experience I'd steer you to Dahua cameras and NVR if you choose to use an NVR. I've found the Dahua equipment to give better image quality for the money, more flexible, and easier to operate. I use a 5216-4ks2 NVR with 10 cameras. All of this IP camera equipment has bugs, but I've eventually been able to work around them. I have a mix of 2 and 4 mp cameras. The 4 mp ones give a bit sharper daylight image if you run the max bitrate, the 2 mp starlights beat them handily in the dark. Fenderman made a good point about the bitrate. If I run a 4 mp camera at the same bitrate of a 2 mp camera, the daylight images look abut the same.
I can't comment about the mobile apps. The warranty issue is "interesting". You can buy grey-market equipment with no manufacturer warranty, which leaves you at the mercy of the seller. Or you can pay a lot more from a factory authorized reseller. I have the sense most of the end users on the forum have gone the grey-market route, without a whole lot of issues as an overall percentage.