wees41It's a 6412 or newer Motorola did not make a 6410.
Correct, for Cox it would be 6412 or higher. The series is DCT-6400, and there was a 6408 (6400-series with 80-gig hard drive) used by other providers, but from that series we used the 6412, 6412p3 (sometimes confusingly called a 6413 by our system and our employees), and 6416. This upgrade also applies to the DCT-3416, DCH-3416, and DCX-3400.
Anyway, the latest Rovi 3.7/Motorola M10 upgrade schedule I have goes like so [in no particular order... 
] :
Completed: Tulsa OK, New Orleans/Baton Rouge LA, Macon GA, Orange County/Palos Verdes CA
Pending: Connecticut, Omaha NE, Kansas/Arkansas, Rhode Island, Hampton Roads/Roanoke VA
If anyone wants to report whether a particular hard drive is successful, I'm sure your fellow users will appreciate it. From around the web, it sounds like just about any eSATA drive is working.