(After I finished writing this, I saw Larry's reponse but I wanted to send it along anyway.)
I just purchased the SMC AWBR but use on my company LAN. The SMC won't assign DHCP addresses on the WAN side, only on the LAN. You'll need to use static IP addresses in order to have the routers connect.
Here's how the IP address assignment should look like per interface.
(Internet cloud or WAN)
DSL router WAN- static or DHCP assigned IP address from your ISP
DSL router LAN- Static address you assign (ex: 192.168.1.1)
SMC AWBR WAN- Static address you assign (ex: 192.168.1.2)
SMC AWBR LAN- Default static address 192.168.2.1 (DHCP enabled here)
Clients on LAN- Receive DCHP addresses from the the range of 192.168.42.2 through 40)
You may not be able to disable NAT and probably shouldn't have to.
I hope that helps some.