4k UHD HDR tv via cable box question

joe2601

Shopping for a new 65" 4k UHD with HDR. I plan on primarily viewing cable television programming via a HD cable box, (Comcast Xfinity X1). I've been reading some negative comments about viewing cable tv programs on 4k UHD tv's in regards to really poor picture quality given the compressed methods that cable companies transmit video. That most cable providers currently don't relay 4k content and that upscaling 1080i/720p via a cable box on large 4k UHD HDR tv's leads to a blurry, sub standard picture, regardless of the model. Is this true?  How is watching 4k UHD via a cable box? My current HDTV has a great picture using a cable box and I don't want to take a step backward. This has me leary about making a purchase. Any feedback is appreciated. Thanks.