I need a backpack for a farm property to primarily blow leaves in the fall/spring and clean out buildings. Want to blow leaves into a pile or back into the windbreak. Probably about 1 acre. I used to rake but it is too time consuming. I hate to pay over $400 (550) vs. $480 for the 600 if I don't need the extra power. How do I decide which to buy? Have never used a backpack before and have a local Stihl dealer where I live. Thanks for your opinions.