I was having problems with the Explorer 8300HDC and Comcast replaced it with a Cisco RNG200. I found a manual for the Cisco 8540HDC/8550HDC DVR and it looks like it is the same as the RNG200.

Anyone know if there is any difference between the 8540/8550 and the RNG200?

Thanks,
Robert

RNG stands for "residential network gateway". It has a cable modem built in. I don't know about the other models you mention but if they don't have it, that's the main difference.