From a previos post, the gateway is 192.168.100.254. I expect the other one is the VIP 1216.
CoryB, did you ever discover the cause for your periodic connection drop? I'm having the same issue and I think I've narrowed down the cause to the fact that I have the 2wire router linked into a 2nd DLink router via the DMZplus address type. The DLink connects all my home networking gear, similar to Dice1111's setup.It is defintely possible to have the 2wire gateway installed in a different location than your VIP1216, this is how my setup is done, although the wiring is a little different than described by others hear.
Your plan to use your existing network should work fine. I had a whole setup of mixed wifi and wired connections going. I had some initial problems as the 2wire firewall was blocking certain ports however I changed the wired connection between the 2wire and my existing network to be in the DMZ and that issue went away. The only issue I am having now is that the Internet connection seems to drop for about 2-5 seconds every half hour. I am planning to talk to tech support to see if they can help locate the cause as this is a new issue for me.
One final piece of advice to keep in mind if you are going for a minimalistic setup, the VIP1216 has an internal green led that flashes pretty much constantly, I think it is a network activity indicator. You can see it through the ventelation holes in the top of the case. It is actually very noticable in a dark room, especially if your tv is off. You may want to take that into account when planning your equipment location.