Get the modem only and then buy the router or switch that suits you. That way you only need AT&T support for the simpler device. One reason to go separate is so that if one component dies you can still use the other. The gateway boxes with both modem and router seem to have the modem fail and then you have to deal with undoing all your network cables to replace it. If it is just the modem, then it is only 3 cables(power, DSL line, Ethernet) that you have to disconnect and reconnect. Security is about the same. If you get a concurrent dual band wireless router, 2.4GHz and 5GHz at the same time, you can run some devices off the 5GHz band to free up the 2.4GHz band for other devices. I set up Vizio and Linksys E4200s so that the iPad/iPod users can get on a less crowded frequency.
reply to bbear2
Put your router behind the 2701.
The WAN output of your router plugs into the LAN of the 2701.
That's what I'm doing (I don't use the 2701 wireless)
I don't game online, so I'm not sure what happens if you game...