This is a little different as well, couple years back I used Asterisk and my ATA/Router device.
- It is different from your setup for sure.
-Basically I connected CallCentric (VOIP) provider to asterisk, then set up the ATA devices to talk to asterisk.

So maybe you can connect asterisk to Vonage then you are set. Asterisk can then connect to a ton of sip and soft devices.

Now that said I read this blog:
https://www.voip-info.org/asterisk-and-vonage/

In the past I considered using Callcentric for incoming and google voice/asterisk for outgoing. ($5 / month ) incoming unlimited
http://nerdvittles.com/?p=26204

Verizon FIOS; all wired as well.

Of course, since Verizon also sold phone service with FIOS, I wondered if there were some QoS games being played with Vonage packets.

However, it's very good to know that fax does work with Vonage. Thanks for information.

If you run asterisk, you can skip vonage. Outgoing calls, require termination service, and you can find it for as little as .01 cent per minute. To have a phone number that calls your softphone, that is direct inward dial (DID), and is usually a few bucks a month to reserve a phone number. There are lots of Termination / DID providers--I recommend flowroute.com. If you still want to use analog phone, you can get a pci card for your computer, with fxo and fxs ports... you plug the land-line into your fxo port, and the analog phones into the fxs ports: your computer will answer the land-line, and bridge calls to whatever destination phone, whether analog fxs phone, or networked softphone, according to a dialplan, which is a text file in /etc/asterisk/extensions.conf.

The DAHDI drivers that run the pci card with the fxo and fxs modules, are stuck in the 2.x.x. linux kernel, which is one of the reasons I switched to softphones (so I didn't have to maintain older kernel just for dahdi.)

It's a pretty powerful application. Asterisk has a fax addon that provides fax capabilities. Extremely large systems might want to combine it with kamailio.

I used to have analog phones to pci card; and then I would have cordless phones plugged into the fxs ports--but that was just creating yet another wireless network in the house, when we already had 802.11, so I switched to just using connected 802.11 softphones (some on laptop, and some on android); now my asterisk box is vps instance, with a tunnel interface (tun0) to vpn, and softphones are on same vpn (a way of having static ip address for softphones that roam from one cafe to the next, and providing a little encryption for calls between sip clients on the vpn)...
I

Sorry to take so long but that was a lot to digest, slac-in-the-box. Wow! That is some serious telephony and I am considering it. If I could drop Vonage the only gain is dumping a small monthly bill as I like the service but hey as Bobby said, "Money doesn't talk, it swears".

Propaganda, all is telephony...

Oh... I forgot about ring, which has so many features, that it has so many dependencies... I tried building it by hand long ago before there was a slackbuild, and I failed... but it was probably just me and not the app.

To this point FIOS puts the ATA adapter at the Fiber NID(at least in my case). Your router is past this and could suffer from buffer bloat. (useful buffers filling to increase max throughput, adding latency to real-time applications like SIP)

So if your application is behind the router QOS optimizations on your router if done correctly could help. I think the gateway router FIOS supplies is weak on QOS settings, but you can use a different router, ((so long as you don't need the COAX to TV capabilities))