Netgear n600

the 300mbps refers to the wireless portion of the router.

if you would have two computers connected via network cable and both have 10/1000 network cards they can communicate with each other at 1000mbps.

if you upgrade your network card, it will allow you to transfer at a rate of upto 300mbps to a wireless device that has a N-wireless.

however, upgrading your network card will NOT increase your internet speed since your internet connection is less than 100mbps