purchase sb6121 a week ago to replace the standard Comcast modem that come with my service charge I 9 dollar a month . I also upgrade to a faster bandwidth from 10mbp to 30mbp for streaming hd movie and such . I have a Belkin N600 Router that I use to get about 6\/7mbps wireless . now I be get on average 14mbp wireless and 35mbp wire !! with this new cable modem it be able to add a additional 5mbp on a 30mbp bandwidth ! my upload also increase from 2mbp to 6mbp . I be very satisfied and quite happy with my purchase . I can now easily stream hd movie now without anymore buffer . I would definately recommend this to my friends\/family . Worth every penny spend .