PCE-AC66 card - not getting 1.3Gbps

[psychopomp1]

Hi
Recently purchased a PCE-AC66 card to use with my Linksys EA6500 router, both of which support AC speeds up to 1.3 Gbps on the 5ghz band. However my desktop pc cannot get speeds any greater than 600 mbps on 5ghz wifi AC. The router is downstairs, pc is upstairs & distance is ~ 5m but walls are wafer thin. If i try to select channel width as 80mhz on EA6500 then i cannot connect to router, however the first time i did this it connected briefly @ 1.3 gbps though web pages didn't load. The only way i can connect to wifi AC is by selecting channel width as 'auto' on the router. I've also tried using different channels on the EA6500 but it hasn't made any difference. The PCI card driver is up to date. I've played with just about every setting on the router so pretty sure there's nothing wrong with it.

My desktop is equipped with an Asus P7P55D Deluxe motherboard (link) which has PCI-e 2.0 slots...perhaps this doesn't support 1.3 gbps speeds? Any advice?
Cheers

 

[thiggins]

Channel width must be 80 MHz (or auto) to enable draft 11ac link rates.

If you are seeing link rates > 450 Mbps, then the card and router are connecting at 11ac rates.

I would get the router and client in the same room, but about 10 feet apart and see if your link rates improve.

Motherboard doesn't have anything to do with it. This is all in the router and client card drivers/firmware.