Simple answer, if you do not intend to do gaming (or other activities that need port forwarding) or banking or buying off the net, then you can use multiple routers, just disable wireless on the RCA.
If you have difficulty gaming or shopping online, you need to have just one router. You may be able to demote the RCA to a bridge, or demote the DLink to being a Wireless Access Point.
Typically to make a router into a WAP:
Sign into the DLink and turn off the DHCP server
then change the IP address of the DLINK to be in the RCA's subnet, but not in it's DHCP range.
then wire the dlink and RCA using LAN ports (often marked 1 to 4) leaving the dlink's WAN or internet port empty.