I would contact Ceton and ask if they have any experience with Mediacom. They're supposed to be helpful with any and all install issues and that should include CableCARD support. I know that they have been in contact with some content providers about their support.
I wouldn't buy an ATI DCT since they never were really supported and they're pretty expensive for a single tuner.
The Ceton is completely useless if you install it in a computer without a CableCARD. Once you get it setup with a CableCARD you can remove the card and it will continue to function as a QAM tuner but not until it has been successfully paired with a CableCARD. I haven't heard a firm explanation for this behavior but a lot of people think it's a Microsoft problem.
I wouldn't buy an ATI DCT since they never were really supported and they're pretty expensive for a single tuner.
The Ceton is completely useless if you install it in a computer without a CableCARD. Once you get it setup with a CableCARD you can remove the card and it will continue to function as a QAM tuner but not until it has been successfully paired with a CableCARD. I haven't heard a firm explanation for this behavior but a lot of people think it's a Microsoft problem.