A 4 lane PCIe switch would allow for a much cheaper board and still be plenty to saturate the available bandwidth. Maybe 2x 2.5Gbe with one hooked to a switch,

A 4 lane PCIe switch would allow for a much cheaper board and still be plenty to saturate the available bandwidth. Maybe 2x 2.5Gbe with one hooked to a switch, plus wifi. Around this price point there are already ARM boards (and passively cooled x86 machines) available much better suited to this kind of use case, like the Honeycomb LX2K.