Unfortunately I'm not able to help, we can't support 3rd party devices. Many people here on the forums have had some luck with wireless AP's and range extenders. Maybe they will have some suggestions for you.
i turned the wireless off on the Arris. i have a trendnet and a d-link connected to the arris via ethernet and they act as AP's. DHCP is provided by the arris. no issues up to this point (knock on wood)
I dont think you will get a response about wireless range unless its something like, "well mine is perfect and I live in a three story house and get good signal everywhere!" But the reality is that its weak as hell and if they arent going to do something about it then at least enable bridge mode. The only reason its not there is because then the dlna server portion wont work properly. Well guess what, i have used it twice after I set it up and havent touched it since. first its to laggy and second there are other devices that do it better. Now I cant speak for everyone but I know many people fed up with weak wireless from the gateway. I have seen b only routers beat this gateway.