Last I heard you could only get an XB6 if you have Gig (400Mbps in the NE). Not sure if that's still a thing though. I'll ask an employee to look into that for you and help you get a 4K box as well.
I've asked a Comcast employee to help you. You should expect a reply in this thread.
Hello Pastorren, I can assist you with getting an XB6 for your home. Can you please send me a private message with your full name, street address, and account number by clicking on my name (ComcastAmir) and then "private message me"?