The SB6141 is a stand alone modem. A Access Point is a wireless router minus the routing. Since the SB6141 can only give out 1 IP, and since AP's don't have NAT, you would only be able to get one device online at a time. Instead you would want the DIR-605L configured as a wireless router. The only exception to this is if you had a class of service that offered multiple public IP's. Even then you would still be limited to the amount of IP's you have, which will probably never be above 8.
Also, any time you change the device the modem is connected to, you have to reset (power cycle) the modem. This allows it to read the router's MAC address and request a new IP for it from Comcast.