There are a couple of problems with that... the first being that wireless traffic is collision traffic... when traffic is on the same channel they'll wait, and go, wait and go.... channels 1-6-11 are the only channels that don't overlap each other.... if you're on #2 and a neighbor is on #1, the traffic won't negotiate, they'll simply go at the same time and have noise interferance, slowing your speed....
The second problem is that wireless connection rate is no indication of true speed. If you want true speed, download LAN speed test, and test a 100mb file copy to a share and see what you get. Odds are you'll find, especially if you live in a city where there are many wireless networks around, that shutting off 40mhz wide and connecting at around 130mbps will probably give you a faster true speed than having it on and connecting at the mythical 300mbps.
I would use channel 6 only, if you look at the FCC report for this router, channel 6 has the highest transmit power.
I live in a congested wireless neighborhood, I don't use 40mhz wide, I use channel 6, I get zero drops, and my wireless actual throughput is FAST. I reboot the router once a month at best. I've also installed it for others using the same methodology and have had no complaints.