As in the previous posts before me, a suspiciously cheap card is sure to cause trouble, there are plenty of fake Chinese clones out there :-).
It can be said that there is a good support for Intel cards under FreeBSD, but not all chipsets are suitable.
It's a question of what you want to use it for in the pfSense?
I350-based cards are perfect, with a smaller compromise I210 and possibly I211-based. (igb4) - https://www.freebsd.org/cgi/man.cgi?igb(4)
As Steve recommended, search for possibly used brand (HP, Dell, etc.) cards based on Intel Ethernet controller.
I would also take into account the recommendation of "bmeeks" (Bill Meeks) for your future use of NGFW:
" Snort Package 4.0 Inline IPS Mode Configuration
IMPORTANT HARDWARE LIMITATION
The new Inline IPS Mode of Snort will only work on interfaces running on a supported network interface card (NIC). Only the following NIC families currently have netmap support in FreeBSD and hence pfSense: em, igb, ixgb, ixl, lem, re or cxgbe. If your NIC driver is not from one of these families, netmap and Inline IPS Mode is not going to work properly, if it works at all."
The question of dual / quad is the extent of usage and the question of segmentation, how big is your network?