I have never had a system, but I think I have a good idea of what I'm looking for...
8 Channel PoE NVR
6 external PoE bullet cams at 2k/3MP+ w/audio
Excellent remote viewing software for iOS
Quiet NVR is a must, as it will be placed in the living room.
I could be talked out of audio, since it's generally listen only and they would be outside.
I would probably add 2 internal WiFi cams at a later date.
My thoughts are the Dahua DAN42B2P from B&H for the NVR with probably a 4TB HDD, but I'm not sure of how loud the fan(s) would be. I like that it has h.265 compression for some future proofing and Dahua seems like a good quality brand from what I've read.
I like the looks of some of the Reolink 4MP RLC-410 bullet cameras. Pretty nice day/night + audio from specific videos I've seen and inexpensive.
If I were to do something like that, would the software for viewing the cameras remotely be a Dahua app, Reolink app or could you use other free or paid apps? Thanks ahead of time!