I have an arris dg2470 router and the 5Ghz is set to auto across 20, 40, and 80 mhz. my internet card is a qualcomm atheros qca61x4 connected through pcie. my phone in the same area on 5ghz gets 150mbps. The only thing that has changed is the hard drive, so I think it is a software issue, however, all of the drivers and windows updates are the same.