majid ,
here i am not using T divider ,
by having RCA OUT CH1 CH2 ,
which is helping Ch3 , CH4 to get power no drops in voltage
i am getting same output on both bridges as if i run single sub
but mono is a perfect amplifier to run any subwoofer
how ever you got only single sub
CLASSAB eats to much Amps to produce same out as MONO
i have seen a pic of power consumption
a comparison between any class AB VS CLASS D
and
another CLASS i found is
CLASS BD which is 85% to 90% efficient on progress