Dude u cannot DSL TWICE.
So, DSLmodem ---> (WHAT)Router, and WHAT cannot be DSL.
If you are lucky this DSL router allows you to ignore the WAN port, make WHAT one of the LAN ports see what happens. No guarantee this will work.
Oh and I assume the DSLmodem is doing NAT. How do u know is doing NAT? you are getting a private RFC1918 IP here. If it doesn't do NAT, then ya, u need a completely different router box.