PfSense as a VMware VM and 10Gbps / 20Gbps
In light of the options out there (Firewall Appliance on VMware), I am considering recommending pfSense as a VM running on VMware vSphere 6.0.
How will pfSense handle greater than 1Gbps as a VM?
If you use server grade network interface chips/cards that support SR-IOV and your CPU/Mobo supports IOMMU then you can have almost (like 95%) native performance.
Without knowing your specs I don't know if it will work, but you could definitely do it with a fast CPU.