For those looking for a T520 solution, there are a myriad of versions marketed and sold under different part numbers. I can usually get a T420 (works just fine if you don't mind PCIe v2.0 or that's all your MoBo supports) for under $50 . . . sometimes as low as $10 shipped!
CAVEAT: These cards run HOT. In my TrueNAS setup, I use the active cooling version of the T420-CR:
Chelsio T420-CR with Active (FAN) Cooling
110-1146-40 C0 (Copper Heatsink)
PCB FAB 100-1120-00 Rev C
110-1146-40 E0 (Natural Aluminum Heatsink)
PCB FAB 100-1120-00 Rev C
CAVEAT: These cards run HOT. In my TrueNAS setup, I use the active cooling version of the T420-CR:
Chelsio T420-CR with Active (FAN) Cooling
110-1146-40 C0 (Copper Heatsink)
PCB FAB 100-1120-00 Rev C
110-1146-40 E0 (Natural Aluminum Heatsink)
PCB FAB 100-1120-00 Rev C
