We upgraded the Intel N-6230 card to their AC-7260 card. In the "Network and Sharing Center" the connection "Speed" rises to 390Mbps, sometimes lower, sometimes higher. The old card never went above 260Mbps. We are trying to only use 5Ghz cus the router is very close to our work area.

However, at speedtest.net our connection speed has now dropped from always being at 60-65Mbps to only 30Mbps. One thing I noticed in the card setting, you can only select "Auto" or "20Mhz" for 5Ghz. I though AC was supposed to be set at 80Mhz.

Drivers Used:
Windows 7 (64)
ProSet v18.21.0 released 11-9-2015
Also tried ProSet v18.20.0 release 9-9-2015
RT-AC66U settings:
Using latest firmware, 3.0.0.4.378.9313.
We have IPv6 Disabled on our router.
5Ghz Settings:
Wireless Mode - Auto
Channel Bandwidth is: 20/40/80 Mhz
Control Channel - 153 (best from using SSider)

However, at speedtest.net our connection speed has now dropped from always being at 60-65Mbps to only 30Mbps. One thing I noticed in the card setting, you can only select "Auto" or "20Mhz" for 5Ghz. I though AC was supposed to be set at 80Mhz.

Drivers Used:
Windows 7 (64)
ProSet v18.21.0 released 11-9-2015
Also tried ProSet v18.20.0 release 9-9-2015
RT-AC66U settings:
Using latest firmware, 3.0.0.4.378.9313.
We have IPv6 Disabled on our router.
5Ghz Settings:
Wireless Mode - Auto
Channel Bandwidth is: 20/40/80 Mhz
Control Channel - 153 (best from using SSider)