I'll second @provels suggestion - I think the i340-T4 provides great bang for the buck. I bought two of these on Amazon (at different times) over the last year and both have worked great (in fact one of them is currently being used in a pfSense box).
https://www.amazon.com/Intel-Ethernet-Adapter-I340-T4-packaging/dp/B003A7LKOU/
If it were me, given the price here and looking at the seller reputation, I'd probably roll the dice on this. But the choice is ultimately is yours. I do recall that one of the i340 I received was actually an OEM IBM version, but again, it has worked just fine.
If you are set on 10Gbit NIC's, I'd also take a look at Chelsio cards which are very well supported in pfSense/FreeBSD. One can find good deals on the T520. I've used both the T520-SO-CR and T540-SO-CR with pfSense without any troubles.
Hope this helps.