I'm about to purchase a new Alpine deck for my winter beater and the existing deck has 2v preouts and the new deck has 4v preouts. Will this make a difference in my amplifier settings or how my system will sound? Any help is much appreciated.
Since you have higher voltage output from your head unit you should reduce the input gain on your amplifier to match the extra output voltage, the net effect of those changes is that noise present in your system will get much less amplified letting you hear more of the music, less of the noise.