By Brandon Matthews
As expected, December auto sales numbers came in stronger than expected. Despite headlines that point to year-over-year decreases for nearly every auto manufacturer, December turned out to be the strongest sales month of year for many auto makers. These include Acura, Audi, BMW, Buick, Cadillac, GMC, Infiniti, Lexus, Lincoln, Mercedes and Porsche. As I stated yesterday, these high end sales are good for Sirius XM Radio (NASDAQ:SIRI) as they result in higher penetra...