I allways believed in the saying "no replacement for displacement" when it comes to cars and wheeling rigs but I am starting to think that there is an end to it when it comes to ATV's. I am starting to consider which atv's I am going to outfit my family with. I get a kick out of my cousins AC 650 H1 turning 27" mud lites but I wonder if there is a significant improvement over a 500? I am leaning toward 550 EFI wheelers either a Yammi Griz or a AC. It seems that there is a point where additional HP only serves to make it easier to break parts and doesn't offer much in the way of getting through tougher obstacles. Not to mention the fuel economy side of the coin. Just curious what people think?