Hello A and B,
A the device you suggested the AC2550 it’s a Router and it won’t work for the scope of this project. Instead we need a wide range expander like the one that I recommended. Thank you for your proactive input.
B, I agree with both of you on buying the device directly from Costco if Costco is able to provide the extended warranty that you have requested. At that price there is no question about. Microcenter offers that device at $ 170 plus taxes, with possibility of extended warranty this is where I quoted you from.
As long as that the model of the device is the same and we can add the extended warranty it makes sense to buy it where is more convenient.