For classic cars that have one speaker hole on the dash, they make these speakers that bolt right in that allow you to play a left and right channel to get stereo out of that one speaker hole. They make two Styles. One style is to separate speakers side by side, and the other style is a single speaker unit with two voice coils. My question is for those who have experience with these two kinds of units, what is the benefit of one over the other? I would like to purchase one but do not have any feedback on the benefits of one over the other.