Alright, we'll do a little math here Say we have a consistent amount of current (amperage) draw at 100 amps and lets Say you were running at 13v. So to find wattage we multiply Volts*Amps 13v*100a= 1300w * .80 (for a Class D amplifier efficiency rating) which would come out to 1040w. So on the opposite side lets say you drop down to 12v 12v*100a=1200w * .80 = 960w In order to gain a noticable increase in output you need to gain at least 3dB. 3dB is the smallest a human can notice a change in output. and in order to gain the 3dB threshold you must in theory double your wattage.. so is that tiny amount of extra wattage going to matter in a daily driving scenario? The short answer is no, it would not matter what-so-ever. SO pick an amplifier that fits your budget, is aesthetically pleasing, and is in your power range. Granted what I've said isn't 100% perfect, but I hope you get the general idea behind it all.