I thought I read that charter was not going to allow people to buy their own modem any more. Anyway there are only a couple of manufactures and you want a docsis 3 device.
After that it really doesn't matter most any router will work with any modem. You just want to make sure the "modem" is only that no router in it, you want to set it to bridge mode and disable the router if you happen to get one.
THANK YOU VERY MUCH YOU HAVE BEEN VERY HELPFUL. HAVE A WONDERFUL DAY !