That’s great many thanks for the recommendationThe I series is best for supporting the AcuSense cameras - the DS-7608NI-I2/8P is what you’ll want. It just works better than the cheaper K series. The K series has a slightly different firmware/GUI to the I series - let’s call it “semi skimmed” It seemed to be developed after repeated issues with the I series “full fat” version 4 being used on it. I’ve installed (and owned for my home system) each of the main NVR versions as they’ve progressed (SE, E1/2, K and I-series) - the I series has been the best of them and I updated to it from my K series when I added a ninth camera.
When you compare the different NVRs using the data sheets they don't necessarily show the real world performance difference - the I series is snappier than the K series especially with the 4K cameras you're looking at.