Introducing Cox Gigablast

I have Gigablast now and I like it. All of my devices connect to the Gigablast Router wirelessly, so I expect some speed degradation from the published rates. My main computer is a Dell Laptop, Inspiron 15, running Windows 8.1, located about 10 feet from the router with no walls in between. The Cox tech told me that my Dell has a wireless adapter in it that is not a dual band, and therefore, the speed tests will show lower speeds than actual. She said that to get the true speed to show on a speed test, I need a wireless adapter that will be the 802.11ac dual band type. I am perfectly willing to buy one of those and to switch it for the original adapter. My question is: will that increase the actual speed, or will it simply allow me to see the actual speed when I run a speed test? Thanks,

Samkrit