If your onboard NIC is working - don't start creating problems
For linux client usage - Realtek gigabit ethernet NIC's are perfectly usable... and even for light duty server stuff (e.g. just on the LAN) - the Broadcom's, need to be careful, as there are a few that use Broadcom's closed source driver, and a few that use their open-source driver, and I've had issues with the open-source driver under RHEL7 with it falling apart under load (unfortunately, the box has 4 of them on the main board - ended up disabling three, leaving one for the ILO/Management interface, and dropping in an Intel Pro/1000 4 port card, which I wasn't very happy about, not for cost reasons, but for performance reasons... (those four ports had to share 1x PCI-e lane, that's all that was available on that box, whereas the 4 broadcom's each had dedicated lanes - and got stuck into a blame someone else loop between the application server provider, HP, and RedHat - no one wanted to take ownership - it'll be a while before I consider Broadcom again in high usage environments)