A specific amp driving a specific subwoofer/speaker/whatever in a specific installation will only get so loud - regardless of the preamp signal of the source.
Stronger signal to amp does not = louder in this context. //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif
What it does = is higher output attained at lower volume settings as opposed to the lower preout voltage that was feeding it before. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif