Bumping an old thread, to note an update. I also have Cox Cable in Orange County. The DCH3416 DVR does work with an external estata hard drive. Currently I'm using a buffalo 1TB esata hard drive. There is an issue with the display freezing up occasionally while the audio continues ok, and anything being recorded will be ok. When there's a display freeze, while recording, I switch to antenna and watch that until the dvr is not recording, then I reboot the box, and it will be ok.
We also tried a DCT3416 with an external hard drive, but it doesn't work. When attempting to "format" the hard drive, the dvr just resets and it never works with the external hard drive.
The other advantage of the DCH3416 is that the firewire 1394 interface works, so you can transfer video to computer with the correct drivers (do a web search for these). The DCT3416 should also work, but it doesn't work with the external hard drive. The DC?3400 black box 1394 interface does not work. I don't know if the Cisco 8462 1394 interface works.