So, when the TV is off, HDMI-CEC is of no use, and you can't control the volume with the remote of your TV.
By sacrificing HDMI-CEC, you lose the option turn off TV, and some other useful bits, BUT... if you program the IR sensor to work with your TV's remote, you can use it for volume control even when the TV is off. That is better than HDMI-CEC for me. :)
Hope you find is useful as well!