I have a very similar set up on 300mbs. sbg6782 modem and a nighthawk x10. I encountered a problem with the the 5g setting on the nighthawk to actually allow the higher speeds. Out of the box it would hit like 30 mbs. Once I spent a bunch of time messing with the frequencies on the 5g, I got it to up the speed. Its consistent with the modem output now at a bout 280-290mbs. There doesn't seem to be any manuals to help with this, but I found the 5g interferes with the 2.4 g. The magic setting I found was channel 153 and mode up to 800 mhz on 5g, and it unleashed the higher speeds.