As others will probably respond Jans45, wireless gateways are generally terrible devices, with their biggest weakness in their router functionality.
The allure is that all the functions are built into one box, but the fact is that few if any gateways do a very good job.
Obviously, the best way to ensure better signal coverage throughout your home is to centrally locate your gateway...however generally, 50 feet is not a great deal of distance to have an issue with.
I would recommend purchasing a quality (not one of the bargain-basement models, regardless of brand!) stand alone router, call Comcast and have them bridge your gateway (which turns off the router capability), and set up your gateway as a regular cable modem, running through your wireless router...ideally, I would locate the router as central as feasible, although with a good router, you may have enough signal coverage.
