So, from what you describe you have 2 WDTV boxes and some external storage of about 12 TB. I am going to guess that your external storage has ethernet also or is inside something that does. So, unless your external storage is more that one box that would be 3 devices. The “no wireless network” issue rules out using the usual 4 port router as they all have wireless built into them these days. What you can to is get an ethernet switch. Switches don’t have wireless built into them and they are cheaper. I just picked up a Netgear 8-port 1GB switch from Best Buy in the past week for my setup for $65. The Netgear 8-port Gigabit Ethernet Switch GS608.
I am also going to guess that you have a laptop or workstation to connect into the network. For what you are doing it probably isn’t worth it to try and create a DHCP server so what you can to is make the IP addresses in each box static by manually entering them into each boxes configuration settings. like 192.168.1.10 for one WDTV, 192.168.1.11 for the other WDTV, 192.168.1.12 for what has your 12TB, 192.168.1.13 for your computer, etc. Just let the netmask entries be 255.255.255.0 and you don’t really care about the gateway since your network isn’t really going anywhere. You could just set them all to something like 192.168.1.2. If you do that then you will also need to use the IP addresses when you try to go to one of them such as selecting the WDTV by the IP address you give it when you stream to it. The WDTV’s are 1GB, make sure the switch is all 1GB also. AND, make sure that you run either Cat5E cables or Cat6, regular Cat5 doesn’t support 1GB and you don’t want that. These cables can go up to 300 feet, depending upon your budget.
There is also a way to manually set up your network so that you can type a name instead of IP addresses. By entering an IP mapping into your “C:\Windows\System32\drivers\etc\hosts” file your computer will know what IP address a name is associated with. For instance, an entry in that file like: “192.168.1.10 wdtv.forward.deck” would tell your computer that if I say to go to “wdtv.forward.deck” I really mean 192.168.1.10.
Hope this helps a little, and thank you for what you do.