Automatic channel selection of WiFi router

I normally have 30 Mbps connection to the Internet via WiFi and VDSL modem.  In the past three days, the speed dropped to less than 0.5 Mbps.  I used a WiFi scanner to scan what channels had been used by my own router and other routers in the neighborhood. Pretty good, due to automatic channel selection, my WiFI router picked channel 9 which was less used.  As things did not improve, I decided to manual assign the WiFi channel.  Channel 6 was selected despite one or two routers nearby were using it.  After rebooting the router, speeds came back to normal.  I suspected that there might be strong interference to Channel 9 due to other devices like Microwave Oven, Bluetooth, Cordless Phone or toys.  The fact is there is no way to make a complaint or seek help since the whole WiFi band is unprotected, free to use by any people and any devices.  Picking the most reliable channel in the junk 2.4 GHz band depends on luck.  Having said that, I am inclined to switch to 5GHz 802.11a band for router and client device provided that the prices drop to average user affordable level.