I used existing coax which had been installed, some by the electrician when the house was built and some by me few years later. None has a rating listed on it but all worked fine with my Hopper installation. All RG6 of course.
If any in your house is RG59, it won't work with any Hopper but will work for Joeys but I would replace any RG59 anyway.
It's too bad there isn't an easy way to know how 'good' the RG6 is, test equipment extremely costly so out of the question.
If you cable is much older than ten years, it may be questionable but may work. Any barrel connectors should be replaced with ones with colored insides. (Don't know how to spell insulators!)
If you really do have questionable cable, you might want to be ready to pull new cable through the attic as the installers probably won't go there. (My attic is a real pain to navigate)