I have not done it but... If you feel like rolling your own, I have seen a recommendation for the Seeed two-Ethernet board attached to a Raspberry Pi Compute module.
Put it in an enclosure, and add a power supply to get a two-port Ethernet router that can run OpenWrt at GBit speed (according to the original 500Mbit+ post). You can keep your Archer C7 as a dumb access point since it has decent Wi-Fi.
This gives you a pretty high-performance router with relatively low power consumption at a very modest price. Have fun!