Novice here: I have a PC and NAS, both with 2.5Gbps ethernet ports. I have them both connected to a 2.5Gbps switch so I can transfer files between them quickly. My only wireless device is an old laptop with 802.11n, so my old Archer C7 router works fine for WiFi.

I'd like to upgrade my internet plan to Gigabit, which will require a new modem. My provider (Comcast/Xfinity) suggests that some Gigabit modems like the MB8600 will only actually deliver 950Mbps and that in order to get the full 1000Mbps, I'll need a modem with a 2.5Gbps port like the MB8611. The price difference isn't much, so I don't mind this, but now I'm worried my router will act as a bottleneck and I'll end up with 950Mbps anyway. I do need to have the router in between the modem and switch, correct?