I am looking at the Ferris IS2500Z w/ 20hp yanmar Diesel but am second guessing myself. Should i step up and get the 31hp Kawi. gas in the IS3100Z? I want 52in deck and the largest property I will mow is 10acers. To my knowlage, there is not a great price diffrence between the two mower but i need the speed of a z and small size of a 52 because of trees and landscaping. let me know which one or recomend another. i need to keep it below 8000 w/o bager.