I can't say for sure what you can do with a miniPC, but I did 1 Gbps routing with all packets going through userland and back to the kernel (because of any over elaborate at&t router bypass) on a pentium g3258 (haswell, dual core, 3.2 Ghz) and it was fine. A transmeta box seems probably a bit old, but relatively few people have gigabit internet. If you wanted that box to do wifi too, that might be problematic; but I generally use wireless routers configured in access point mode to be access points. In access point mode, as long as the networking hardware and drivers are decent, you get fine performance; you don't need great NAT acceleration or properly managed memory for state tables on the wireless devices, since that's managed on the router/firewall/could be a home server too.