Though CetonCorp says use GigaBit, I have used a spare / older Verizon AT router as a bridge only for a single extender. Ethernet to MOCA and no WAN. Just make sure your second Actiontec does not conflict with the first ones IP. Set it for a different IP like 192.168.1.2 or something other than what the main Actiontec router uses, and something outside of your DHCP range. Since the amount of broadcast / multicast traffic from the Mediacenter network and extenders seemed to be rather high, I went ahead and ran CAT6 cable. But I also run a 6TB RAID file server for personal media. I also now have a Quad Core Server 16GB of ram, 2 TB of storage, with two Ceton InfiniTV PCIe for a total of 8 tuners and 5 extenders. So my network is rather pushing it over a 16 port layer 2 managed switch, and the remaining Actiontec only runs for Ethernet WAN traffic to the Internet on the ONT. No coax on the routers. I now have no Verizon TV hardware.
When I first started with only two extenders, the MOCA bridge worked fine over coax to single Echo extender. Actually at one point I had two OLD Actiontec routers set up as bridges to two seperate extenders before I pulled the CAT6. I hope this information helps.
Remember the limitations of MOCA 1.1 175 Mb/s and 2.0 at 500 Mb/s which I am pretty sure the Actiontec routers are at 1.1 with a limit of 175 Mb/s. Though I could be wrong. So if you plan on more than 1-2 extenders over coax, I would say it will not work.
If your existing router is not a GigE router, but one of the Older routers like a Rev A-D or possibly E or F, Verizon may replace it at no cost. You would need to contact tech support and consult with the regarding wireless speeds and other issues you may have regarding gaming speeds and router locking up etc..
If they replace your existing router, there is a good chance they will not want the old one back. If that is the case, you have a cheap bridge right there at no cost. Since you would not be using the firewall or NAT features and WAN port. It should work fine for a single extender. Remember if you have Verizon hardware on the MOCA, you could run into trouble with your STB hardware.
IT IS BEST TO RUN GIGABIT AS RECOMMENDED.
Also items to consider. The Ceton Echo is still not running Android!!!! So that means no internet apps, such as Netflix, Etc. My daughter runs X-Box 360 that works well, and I am running two PCs as extenders, in addition to the server at the main TV. So they have Internet. But the 2 Echos in the kitchen and Master Bedroom do not have all the features I would like. Also need Windows 7, or the Beta Firmware and Windows 8 with hopes it works, I have not tested it, but I am running the tuner pool with all beta software and firmware in current configuration with no trouble under Windows 7.