As it stands you know what works best. Go with that.
Remember the router has to work hand in hand with the modem so all it means is one combo is better than the other.
Try telling make and models and if the router firmware is current.
I have 2 modems, if I connect it like modem#1>pc I get 950mb down, modem#1>router>pc=950, modem#2>pc=950, modem#2>router>pc=no more than 650. So what is the problem? is it router? but it works with modem#1. is it modem#2? but it works directly to pc.

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