I found an earlier post by Richard42 very helpful, where he described how he got a Linksys wireless router to wiork with the RTA1320. In the same spirit, I'm offering these notes on how I got my EDIMAX router to work with the 1320.
I ended up taking a slightly different approach.
The main thing was to set the RTA1320 to "Bridge" mode - meaning it effectively stops trying to be both a router AND an ADSL modem and just acts like a modem. To do this, consult the Dynalink website: http://www.netcomm.com.au/products/dynalink/rta1320/troubleshootings/how_to_bridge_my_rta1320?SQ_DESIGN_NAME=support&SQ_PAINT_LAYOUT_NAME=faq . Then go into the EDIMAX set up and set your xDSL connection method/parameters according to what your ISP advises (here in Oz I'm using PPPoE).
The Dynalink default IP address is 192.168.0.1 and the EDIMAX default is 192.168.2.1. Now, in theory that should be fine but - as it happens - the EDIMAX address clashed with the default address of a separate Apache installation that I have for running PHP scrips. Anyway, that's a little beside the point...
The key thing then was to change the EDIMAX default IP address and range to something else that didn't conflict with either the Dynalink IP or Apache IP. Taking Richard's lead, I set the default IP address for the EDIMAX to 192.168.0.1 and the range from 192.168.0.100 thru 192.168.0.200. That seems to have done the trick!
Hope this saves someone some brain/heartache...