Paying for Gigablast and getting Kilobytes

speedtest.net, cox.com's hosted speedtest also. Both give the same result. sub 150 Mbps

No packet loss, low latency, low jitter, LOW speed.

I don't know what equipment you have...such as separate modem and router...but are you hardwired to either device with all other devices disconnected from your LAN while testing?  You want 1 testing device to be the only device on your LAN.

Hardwired Motorola MB8600 (3.1) to Netgear AC1750. Hardwired now only to the desktop. Testing from desktop. (I disconnected all other wired devices from the LAN) Still getting the same poor speed. Up until mid-July I was getting 700Mbps down testing from wireless or wired devices. Something changed and it wasn't on my end.

Are you suggesting I disconnect all wireless from the LAN then test again? I will, but not sure what we're doing here. The problem is what is/isn't coming in to my home, not what's going on inside of it. Cox notified us of network service being performed yesterday. That got my hopes up. Nothing changed. 

Looking for other options in Mesa, AZ.

We want to test the bandwidth coming to your home.  Only 1 device should be solely connected to this bandwidth.

Disconnect the Netgear from the Motorola and connect desktop to Motorola.  If you don't get a connection, you may have to reboot the Motorola.

Once your desktop is connected, run speedtest a few times from a few sites at a few intervals.  This will give you an idea what bandwidth Cox is providing you.

I'm not doubting you're not getting gigabit.  We just need accurate samples.