QQKLTB :
just in case you are thinking twice as much power will be twice as loud,it's not true!
i'll save my boring,possibly incomplete explanation and recommend a google search on sound pressure level.and somewhere there is a chart that shows everyday sounds,types of music,power levels required to reach pressure levels with a variety of speaker sensitivities in a typical room.it's actually informative.
don't want to see you go buy a 400 watt amp(per side) and realize it's not that much louder.although if your subs weren't powered it would probably make a bigger difference,but that's not the case.