Wired ethernet speed slow Orbi 850

The cable modem is a Netgear Nighthawk CM2000 which is definitely doing its job because our wifi speed is 1400+ next to the router and quite fast everywhere else. Wired ethernet to a pair of new iMacs has never made it past 325. We've been using the wifi for the iMacs until the fix, and that gets them in the 700 range for download speeds.

The firmware version is the absolutely latest one which is of course not always the best, but it is indeed the latest because tech support had me install it two different ways. It is this: RBR850-V4.6.9.11_2.3.5-signed.chk Tech support btw was two different people on chat and one person on the phone and they were all intelligent, patient, good at their work.

Yes everything has been powered off and on several times, the paperclip restart from factory default tried, all sorts of tweaking in the admin done as led by tech support. All this must happen before being bumped up to level 2 support who have not yet called me back but this being a weekend, I am not impatient for that or put out by it in any way and understand these things take time. 

In the meantime I have found the solution on my own! First step is to carefully remove all attached cabling, next put it back in the box and return it to Amazon from whence it came, and finally replace it with an Asus Zen AXE11000 as god intended. Whichever god you like.