I would agree that "cheap, Chinese" x86_64 boards are perhaps not the best choice for a critical piece of infrastructure. I presently use PC Engines APU2C4 and APU3C4 boards and find they have low power consumption (under 10 W running a desktop distro including dual Samsung SSDs under ZFS), reasonable performance, and very good reliability. Their processor, however, is not as powerful as other options available today.
There are more powerful options (that I have not personally used, or are "as rare as hens' teeth") out there at moderate cost, such as the offerings from https://fit-iot.com/web/, https://up-board.org/, https://www.hardkernel.com/shop/odroid-h2/, and a couple others that I can't find links to right now.
The benchmarks that @oslyak provided are insightful. The FX-8320 is probably a good point of comparison, as isn't a "screamer", with single-core Passmark performance as one measure of around 1400. For comparison the AMD Ryzen 5 2600x has single-core Passmark of 2143.
I can't provide further recommendations as I don't own any of the newer, better quality, x86_64 boards. From what I have read, the WRT32X seems to be a solid unit. In Top ten routers currently in use?, slh states
Both mvebu and x86_64 can be used for 1 GBit/s WAN speeds.