x86 is crazy fast in many ways. However with x86 you need PCIe cards and not PCI if you want good throughput. Cheap PCIe cards don’t have very good throughput either, I prefer Intel cards. and a dual core 3Ghz does very well. However a 1100AH or X2 will do 1Gbps just fine providing your not bogging it down with excessive firewall filters or vlans.