There appears to be several issues here.
My husband wants to get ride of cable, go to various streaming services and save money on the cable bill.
That's your right of course, just be aware that you may not save as much money as you think - this will require a good deal of assessment on what partlicular shows you want to watch, whether you have OTA (Over the Air) broadcast service available in your area, and what your internet service tier is. That's beyond our scope and you'll have to make that determination separately.
The wifi in our house is horrible. We have the Orbi system and we have all three units set up. We have a space with three TV's that all run at the same time. Our wifi can barely handle one tv, three is a no go. This is in addition to the rest of the TV's in the house. The house is an older house and wide.
Mesh systems like the Orbi work best in a "star" configuration, where the main device is in the center and the satellite devices radiate out from the center, to cover the most area. You could try moving the Orbi units around to better get coverage.
As far the older house issue, you might have wire mesh behind plaster walls, and those would defnitely be detrimental to WiFi.
If you still can't get decent WiFI reception after all this, then you will have to go with a different solution. Aside from the excellent suggestion above to go with MoCA adapters, you can also: 1. Run Ethernet cables from the main Orbi device to each of the satellites so as to improve communication between each unit; or if that's not enough,
2. Use Powerline adapters, which use your home's electrical wiring to carry internet,
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