If your going to be going PfSense, do know that PfSense will eventually be requiring a cpu that supports AES-NI with version 2.5. That's a while off, but its good to know so that your not buying hardware that eventually will require a replacement with a PfSense update.
With that in mind, you can do something like this:
Its complete overkill in the cpu department for a 100/50, but it gives you a lot of headroom to support higher future speeds or a ton of packages. The motherboard provides two very nice Intel ethernet ports, as well as an Intel wireless card. That allows you to do a standard network plus wireless all on one box. Nice. You also have a full 16x pcie lane to throw in another ethernet card for whatever you desire. You could grab something like an Intel Pro/1000PT quad port off of ebay, if you want to build out a more complicated and robust network.
Usually, you'd just have one ethernet out of your router which you would feed into an ethernet switch, which will offer more ports and expand-ability. That would be something like this:
When you buy an off-the-shelf "router" from a store, its actually a combination of a couple things. Those units combine a switch, an access point (which provides Wi-Fi), and the "router" functionality of handling the firewall and DHCP server functions.