SB6183 with Ultimate

I got a new SB6183 to get the 300Mb speeds that I pay for. I'm not getting any faster than I was with my old SB6141 modem (about 170Mb down). I keep reading that something has to be done on Cox's side to enable the faster speeds for my new modem. The support people I talked to had no clue what I was talking about and is trying to send a tech out. Does anyone know if I should automatically get the faster speeds with my new modem?