Adding a second router to network. Can I give it a public IP address?

I just bought an Asus RT-N66W router. It has plenty of great features which I would love to use. One of those features is using a DDNS server.

The issue is that my Asus router has a private IP address given from the AT&T Uverse Modem/Router.

Idealy I would like to disable DHCP entirely on the uverse box and just serve the public IP address to my Asus router.

I called AT&T for support. They quickly transfered me to support line in which I would have to pay +$16/month. (?!?!) For them to help me.  

Network Setup

Internet > Uverse Box > Asus Router > Computers

For the moment I've placed the router in the "DMZPlus" zone. so that I am at least not going through 2 firewalls. 

I've been wondering if the Cascaded Router feature might help,

Is there something I might be missing? 

This was much easier to set up back when I had Time Warner...