thats theoretical

you need double the power or double the area (cone size) to see a gain of 3bd's.

it als takes 3db's for hte human ear to notice a difference

and yes you can bridge ANY 2 channel amp.

heres how to do it on an amp that does not support bridging, you can even do it with 2 amps if you want

in order to unders tand how an amp works you need to know that it is a push pull AC current, all an amp does is take DC and convert it to AC.

you wnat 1 amp to push and the other amp to pull (or channel) so to do it you need to run one of the maps out of phase.

basically do this take 1 RCA and put it to one amp then take the other side of the RCA and run it to a crossover in FULL mode with it out of phase, this giving 1 amp a in phase signal and the other amop an out of phase signal

then you take the + of the first amp and wire it to the + of the sub, then you take the - of the first amp and hook it up to the - of the other amp, then you take the positive of the other amp and put it to the - of the sub.

the reason that you need to put the - of the first ampt ot he - of the second amp is because both amps need to share the same ground.

FYI i have extensive knowledge in car audio, i used to compete heavily in MECA and was sponsored by a very well know company and have several trophoies to prove it.

theres not much about car stereo that i dont know