While I'm leery of boosting the transmitter power (noisy signal and stress on the components), getting the extra WiFi channels in the US would move your usage slightly outside the range of most home WiFi networks. They overlap channels 8 through 11, but you get some bandwidth space.
Channels 12 & 13 are allowed in the US, but only for low power usage. These two channels overlap with channel 14, which is forbidden to use in the US. I don't know what uses channel 14, but some people think it's used for military communications.
Channels 12 & 13 would probably be safe to use out in the woods, but I wouldn't want test them near anything military.