Hello @jperrywinters 

 Range extender receives data from the router wirelessly and then forward it to the Wi-Fi network clients and speed will decrease during the transmission.

• For dual-band RE, test 5Ghz Wi-Fi band of range extender when perform a speed test. For RE220 the maximum Wi-Fi Link speed is 433Mbps
• Try change router 5Ghz band to 80Mhz.
• You could refer to the thread below to troubleshooting

 What should I do if Internet speed becomes slow via Range Extender?

Can you help  provide some  information below to check if the speed is reasonable:

1. Speed test result from router's  at the RE's location, this is to check how much speed range extender could receive speed from router ; Wi-Fi  link speed  (How to check the associated/link speed on a wireless client)

2. Speed test result of RE's 5Ghz Wi-Fi  & Wi-Fi  link speed 

Thank you

Hello   @jperrywinters 

Thank you for more case details. As Range Extender works in ' half-duplex ' mode in extender mode,  it can only talk to the main router or the wireless client device in either way, not the same time, the link speed at physical layer will cut to half. On the other hand, the actual speed test could be around 40%-60% of wireless link speed due to overhead in the communication.  Here is an article explained the actual speed and link speed,  Why isn’t my Wi-Fi as fast as advertised?

Thus in extender mode, we use range extender mainly to increase the Wi-Fi coverage in wifi dead speed, not increase speed. 

In your case, if router speed is around 330Mbps, range extender speed working in extender mode might not very ideal.  To boost speed or get ideal speed, would you consider an Ethernet connection? To get better speed in the basement & TV requires an Ethernet port, you might  consider wiring a second Gigabit Router to the first router via Ethernet cable and use it in AP Mode. 

Or it is recommended to consider an AX Range extender, which has a chance to negotiate at higher link speed with router and improve performance, but kindly note that extender will also work in half duplex and speed also reduced in a wireless transmission.