Buyers of x540 chipsets will want to know they are 1Gb/10Gb. They don't do 2.5Gb or 5Gb.

I have an x540-T2 in my firewall and it's performant if hot. I keep a fan on it.

I run one 10G to one of these for places where I have machines with 2.5G NICs: https://www.amazon.com/dp/B0CJMTT9DF