Comcast 4-Tuner CableCARD, How can I get one

I went to the local Comcast office and they said Comcast doesn't offer 4 tuner cards, only 2 tuner. I called multiple numbers and got the same story that Comcast doesn't have more than 2 tuner cards. So I have my Romio plus and how do I go about getting a 4 tuner card that works with Comcast?