Unless I'm missing something, 10G will still require an extra mini-PCIe adapter for a 10GbE NIC. The PC Engines APU2 only has 1GbE ports and no full size PCIe slots.
This is probably too late to suggest, but the new the Intel Atom C3000 (Denverton) series would have been perfect as an Atlas Anchor. Supermicro has 10GbE boards with QuickAssist for under $500 USD.