I have the Cox Panoramic gateway (modem/router combo). I also have a particular area of the residence with lousy WiFi (my room, as it happens). The house had recently been centrally rewired with cat5e ethernet and coax cables running from four locations and terminating in a wall panel, connected to the Panoramic gateway.
For a $179 installation fee plus an extra monthly payment Cox offers "WiFi extenders". I've no idea if they're b/g/n or ac. As it happens I had a 6-year old 'n' model Apple Airport Extreme which I have connected with one of the cat5e ethernet cables in my room. The other end of that cable is plugged in to the Panoramic gateway. In Apple talk this is called putting the Airport Extreme router in "bridge" mode. Since I use my laptop a little more than 10 feet away from it I get superb signal strength (never below 88%). Since the Airport Extreme comes with 4 LAN ports, I use one to feed my Roku, thus eliminating the need to rely on a fluctuating WiFi signal for that device.
Providing your Netgear CG4500BD is a Cox-approved device I would imagine you could configure any *current*, 'decent' (read: not cheap) n or ac router of your choice to work in a similar fashion.
