@coastman49,

Unfortunately, Yes, this is just the nature of range extenders. REs will repeat the signal and due to this suffer from something called half speed, which essentially cuts your speed in half initially, and then you lost additional bandwidth due to the overhead that naturally comes with wireless connection and from environmental factors/interference. This is why APs are the absolute best choice, because the wired connections do not suffer from any of these factors.

Looking at the models that you provided, your RE and your router are both capable of creating a OneMesh Network, which is far less affected by this and will provide a more seamless experience, especially when a device is in between the different nodes of the network and roaming. I recommend setting your AXE75 to connect to the RE via a Onemesh Connection

The Network Cards that you have listed are only Wi-Fi 6 Cards, not Wi-Fi 6E cards. This means that they do not have access to the 6Ghz range. For most users, the 5Ghz range provides more than enough bandwidth, as the 5Ghz band has been optimized so much since it first came out and can reach multigig speeds.

  @coastman49,

Right Now, we only offer two different Wi-Fi 6E PCI-e adapters, as most users will not see an increase in speed when adding Wi-Fi 6E to a client connection. Keep in mind that Wi-Fi 6E operates at a higher frequency and, therefore, cannot travel the same distances and is more prone to interference.

Something to keep in mind is that your RE doesn't support the 6Ghz band, so your second PC would need to connect all the way down to the AXE75 to use the 6Ghz band. Your RE will also be limited 5Ghz speeds since it cannot build a 6Ghz backhaul, meaning that a Wi-Fi 6E client could potentially be bottlenecked at the 5Ghz RE speed. For this reason, I can only really recommend upgrading your basement PC.

I would recommend moving the RE closer to the router; the ideal placement is usually closer to the midway point between the devices. If the RE is limited in its bandwidth due to having poor signal, that will also be reflected in the clients connected to the RE, and may force devices to connect directly to the AXE75. 

  @coastman49,

Due to the nature of how Range Extenders extend the network, this is an expected speed for the connection.

You may be able to improve the connection further by setting the devices up as a OneMesh network rather than as a traditional Router and Range Extender Combo. You May Also Consider checking to see if your devices have been updated for EasyMesh as this can sometimes provide a more flexible setup than onemesh can.