My first question is, do you really need 4x 10Gb ports on the router?
The reason I am asking is what you list as your requirements.
You’re in an office environment and you state that you have 2 switches, a server and a NAS.
Which then would lead me to ask additional questions.
Are your switches stackable or are they acting as two independent switches?
If they’re independent, are they serving two parts of the network that need to remain segregated from each other or are they linked into each other?
The reason I ask this is it sounds like you may be confusing pfSense with an all in one home router. All in one home routers aren’t strictly routers, they’re a monstrous amalgamation of a router, rudimentary firewall, a switch and access point. pfSense and the hardware netgate offer are just firewalls/routers (with the exception of the SG3100).
Each port is a separate network to another unless you setup LACP and port bind interfaces (which requires compatible switches or host machine setup).
For the sake of simplicity and management you would be better to take two ports (or just one if you’re switch doesn’t support LACP) from the router to a switch. (Or one to each switch if you have a stacked setup (it helps with failover)). Then use VLANs from the switch to the router if you need to restrict access from the network to the server and NAS. This leaves your switch doing switching and your router doing routing and firewall.
If you want a better idea of what I would recommend doing, please give some additional information regarding what switches you have, what your network topology is and how it is separated (eg Subnets).
If all you’re interested in is MOAR PORTS on the XG-7100, it does have a PCI-e x8 expansion slot that you could drop in something like an Intel X520-DA2 for an additional 2x 10Gb SFP+ interfaces.