It should be. Why do you believe you need to add a network card?
I have 100mb/s up and 100mb/s down but when i download anything i get capped at 10 mb/s while on wired connection through the motherboard. my brother on the same ethernet gets around 60-70 mb/s download on his xbox one. I just assumed that the xbox has a better network card and that mine is capped at 10mb/s