2Wire doesn't make it easy to add another router.
I found this helpful off the web:
1. Set your router's WAN interface to get an IP address via DHCP. This is required at first so that the 2Wire recognizes your router.
2. Plug your router's WAN interface to one of the 2Wire's LAN interfaces.
3. Restart your router, let it get an IP address via DHCP.
4. Log into the 2Wire router's interface. Go to Settings -> Firewall -> Applications, Pinholes, and DMZ
5. Select your router under section (1).
6. Click the DMZPlus button under section (2).
7. Click the Save button.
8. Restart your router, when it gets an address via DHCP again, it will be the public outside IP address. At this point, you can leave your router in DHCP mode (make sure the firewall on your router allows the DHCP renewal packets, which will occur every 10 minutes), or you can change your router's IP address assignment on the WAN interface to static, and use the same settings it received via DHCP.
9. On the 2Wire router, go to Settings -> Firewall -> Advanced Configuration
10. Uncheck the following: Stealth Mode, Block Ping, Strict UDP Session Control.
11. Check everything under Outbound Protocol Control except NetBIOS.
12. Uncheck NetBIOS under Inbound Protocol Control.
13. Uncheck all the Attack Detection checkboxes (7 of them).
14. Click Save.
Your router should now be able to route as if the 2Wire was a straight bridge, for the most part.
The only addition I needed to make was to add a DNS server. Google offers: 188.8.131.52 & 184.108.40.206
Hope this helps