I am buying my first EXMARK (gear drive) walk behind mower & can't decide on which Kawasaki engine to get!! - On the 36" fixed METRO walk behind (gear Drive)is 12.5 kawasaki enough? or is 15 hp necessary and why? - On the 48" fixed is 15 enough or 17hp? - Do you need more Horsepower when running a 36" or 48"floating deck vs. 36" or 48"fixed THANKS for all your help!!!!!