Ok. I was looking through my 2008 Sthil Catalog because I need to purchase a new trimmer and blower. I will be using it for 10-20 yards a week for no more than an hour a day. Heres my question. What is the difference between say the KM 55 R kombi motor and the KM 90 R kombi motor. The 55 is a "HomeScaper" unlike the 90. Is there a big difference? Same with say the BG 55 and the BG 65 D? Thanks in advance.