Dual nic for opnsense build

I'm putting together a budget opnsense build...my first one. I picked up a used HP t740 thin client which has an x8 pci slot.

I need to put a multiport nic in it and am looking for recommendations. Right now I have 600mbps WAN but hoping to upgrade to 1g+ fiber soon. So for future planning a 2.5G nic would probably be a good idea. Heat may be an issue with high consumption cards in this form factor.

Hoping to keep it under $50

Thanks!