Looking at the graphs, you should start all the axes at zero. if you start it at 50 decibels then it visually exaggerates the differnce between the 2 cards. Remember that a graph is supposed to show a visual comparison between the objects being benched. You basically forcing people to say,"Hey the stock one is 6 times louder than the oc one, oops, I didnt see that the graph starts at 50dB, so that means it is, umm, 60/50, and um taking into account that dB are logarithmic, uhm, let me get a piece of paper". i.e. an extra level of confusion.