The XPS 8900 driver page does not show a driver for the 9260. This means that we never tested it. In theory, it could work with a driver directly from Intel. For my notes, send me via Private Message the XPS 8900 service tag number.
Easiest way to upgrade wireless is to buy a usb a/c wireless network adapter and disable your internal wifi card. No internal installation needed. You already know that you need a compatible wireless a/c router to upgrade to a/c. That's the expensive part. You might reconsider upgrading when pricing those.
I bought TP Link T2U adapter and it is being useless. Really slow. in the description, they mention it supports really fast speed but NOOO. I have Spectrum Wireless Router
Sagemcom F@st 5260
it will work with Intel 9260 AC card?
You have to have an 802.11 AC ROUTER to go along with any adapter.
Easiest Pain Free way is usb AC600 adapter.
Plug in to any usb port and use immediately.
If you get the right one there are no drivers to install you just reboot and done.