I've seen lots of pretty terrible experiences with the i40e and newer Intel drivers.
For newer NICs than the X520s I'd probably grab a Connect-X card.
For newer NICs than the X520s I'd probably grab a Connect-X card.
Looks like prices on the E810-XXVDA2 have come up since the last time I looked while prices on the ConnectX-6 Lx have come down, so that'd be a good option!