Slow download speeds

I have been trying to run Kodi on one of my 2 new Raspberry Pi 3s. My upstairs TV, it is nearly impossible. When I run a download speed test, it is performing at 2-3 mbps. When I sit my Samsung Galaxy Tablet next to it and run the download test the tablet is getting 25 mbps reliably. Does anyone have an answer for this or any suggestions?

Do I need a usb wifi antenna for the Pi?

To help boost performance I even purchased a new Netgear Nighthawk router.

I am kind of desperate here (and not all the techie). TIA!