Replacement wireless unit (intel centrino advanced-n 6235)

In my UX31A-DB51 I have the 'Intel Centrino Advanced-N 6235' wireless (WiFi+Bluetooth) card.

It supports up to 300 Mbps speeds which became odd after I purchased the Netgear AC1900 router (which is connected to my master machine via a gigabyte port). I want a higher homework speed to/from the UX31A.

Browsed quite a bit and I took it that the N6235 module in the UX31A may be based on the PCIe M.2 slot (not sure if it's true). Also read that the Intel Dual-Band Wireless-AC 7260 may be a workable replacement, but it only provides up to 876 Mbps speeds. There have been further wireless modules by Intel, but I am confused as their description is too narrow.

Can you suggest any replacement wireless module to N6235 which could deliver up to a gigabyte home network speed? Thanks in advance.