The 2005 Porsche Boxster is available as a 2-door, 2-seat convertible. Starting at $43,800, the 2005 Porsche Boxster Base (M5) is powered by a 2.7L , 6 -cylinder engine mated to a manual transmission that returns an EPA estimated 20-mpg in the city and 29-mpg on the highway. The top of the line 2005PorscheBoxsterS (M6) , priced at $ 53,100 , is powered by a 3.2L , 6 - cylinder engine mated to a manual transmission that returns an EPA estimated 17-mpg in the city and 25-mpg on the highway.