Hikvision ColorVu are good value for your money, not too sure what resolution your DVR can handle, signals switchable TVI/AHD/CVI/CVBS and colour at night.
When My previous Samsung failed I purchased Samsung HRX 821 (on their suggestion, bad mistake) to keep wiring and cameras already installed.
Now two of the cameras have failed SDC 9443vBCP they don't make these anymore so looking for replacements hoping to keep DVR and installed wiring & cameras.
I really would like to purchase just two cameras
Hoping not to have ditch what I have and start again.